sunxi: mellowflyc5: port U-Boot to v2026.07

This commit ports the Mellow Fly-C5 board support in U-Boot to the newer
v2026.07 branch.

What was done:
1. Removed `BOOTPATCHDIR="u-boot-sunxi"` from the board configuration file
   `config/boards/mellowflyc5.csc` to inherit the family default U-Boot
   directory `v2026.07-sunxi64`.
2. Deleted the legacy and incompatible U-Boot patches under
   `patch/u-boot/u-boot-sunxi/board_mellowflyc5/`.
3. Created a new porting patch `001-mellowflyc5-dts-and-defconfig.patch`
   under `patch/u-boot/v2026.07-sunxi64/board_mellowflyc5/` supporting
   OF_UPSTREAM:
   - Added the upstream-aligned device tree under
     `dts/upstream/src/arm64/allwinner/sun50i-h618-mellow-fly-c5.dts`.
   - Updated `configs/mellow_fly_c5_defconfig` to map all DRAM configuration
     variables to the newer `DRAM_SUNXI_*` names (e.g. DRAM_SUNXI_TPR0,
     DRAM_SUNXI_TPR10, etc.) and set the default device tree to
     `allwinner/sun50i-h618-mellow-fly-c5`.

Why it was done:
U-Boot for the sunxi64 family has moved to `v2026.07`, which uses the
`v2026.07-sunxi64` patch directory. Keeping legacy patches in the old
`u-boot-sunxi` directory was causing build failures because the old patches
were incompatible with the newer U-Boot structure.

Captured boot serial log (compiled with uboot-swig-fix):
```
U-Boot SPL 2026.07-rc4_armbian-2026.07-rc4-S1296-P5b04-H1daf-V0a73-Bb190-R448a (Jul 12 2026 - 16:57:38 +1000)
DRAM: 1024 MiB
Trying to boot from MMC2
NOTICE:  BL31: v2.12.9(debug):armbian
NOTICE:  BL31: Built : 02:30:58, Jul 12 2026
NOTICE:  BL31: Detected Allwinner H616 SoC (1823)
NOTICE:  BL31: Found U-Boot DTB at 0x4a0b4fc8, model: Mellow Fly-C5
INFO:    ARM GICv2 driver initialized
INFO:    Configuring SPC Controller
INFO:    Probing for PMIC on I2C:
INFO:    PMIC: found AXP313
INFO:    BL31: Platform setup done
INFO:    BL31: Initializing runtime services
INFO:    BL31: cortex_a53: CPU workaround for erratum 855873 was applied
INFO:    BL31: cortex_a53: CPU workaround for erratum 1530924 was applied
INFO:    PSCI: Suspend is unavailable
INFO:    BL31: Preparing for EL3 exit to normal world
INFO:    Entry point address = 0x4a000000
INFO:    SPSR = 0x3c9
INFO:    Changed devicetree.

U-Boot 2026.07-rc4_armbian-2026.07-rc4-S1296-P5b04-H1daf-V0a73-Bb190-R448a (Jul 12 2026 - 16:57:38 +1000) Allwinner Technology

CPU:   Allwinner H616 (SUN50I)
Model: Mellow Fly-C5
DRAM:  1 GiB
Core:  71 devices, 23 uclasses, devicetree: separate
WDT:   Not starting watchdog@30090a0
MMC:   mmc@4020000: 0, mmc@4022000: 1
Loading Environment from FAT... Unable to use mmc 1:1...
In:    serial
Out:   serial
Err:   serial
Allwinner mUSB OTG (Peripheral)
Net:   using musb-hdrc, OUT ep1out IN ep1in STATUS ep2in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
RNDIS ready
eth1: usb_ether
```

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Assisted-by: Antigravity <antigravity-ai@google.com>

Author: deece

config/boards/mellowflyc5.csc

@@ -1,6 +1,5 @@
 # Allwinner H618 quad core 1GB RAM SoC 100M Ethernet WiFi
 BOARD_NAME="Mellow Fly-C5"
-BOOTPATCHDIR="u-boot-sunxi"
 
 BOARD_VENDOR="mellow"
 BOARDFAMILY="sun50iw9"

patch/u-boot/u-boot-sunxi/board_mellowflyc5/0002-add-defconfig.patch

@@ -1,19 +1,58 @@
-diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
-index 99f97d5..5392fd2 100644
---- a/arch/arm/dts/Makefile
-+++ b/arch/arm/dts/Makefile
-@@ -1,4 +1,5 @@
- dtb-$(CONFIG_MACH_SUN50I_H616) += \
- 	sun50i-h616-orangepi-zero2.dtb \
- 	sun50i-h618-orangepi-zero3.dtb \
-+	sun50i-h618-mellow-fly-c5.dtb \
- 	sun50i-h616-x96-mate.dtb
-diff --git a/arch/arm/dts/sun50i-h618-mellow-fly-c5.dts b/arch/arm/dts/sun50i-h618-mellow-fly-c5.dts
+diff --git a/configs/mellow_fly_c5_defconfig b/configs/mellow_fly_c5_defconfig
 new file mode 100644
-index 0000000..2f2daa7
+index 00000000000..84f142dd689
 --- /dev/null
-+++ b/arch/arm/dts/sun50i-h618-mellow-fly-c5.dts
-@@ -0,0 +1,118 @@
++++ b/configs/mellow_fly_c5_defconfig
+@@ -0,0 +1,43 @@
++CONFIG_ARM=y
++CONFIG_ARCH_SUNXI=y
++CONFIG_DEFAULT_DEVICE_TREE="allwinner/sun50i-h618-mellow-fly-c5"
++CONFIG_SPL=y
++CONFIG_DRAM_SUNXI_DX_ODT=0x07070707
++CONFIG_DRAM_SUNXI_DX_DRI=0x0e0e0e0e
++CONFIG_DRAM_SUNXI_CA_DRI=0x0e0e
++CONFIG_DRAM_SUNXI_ODT_EN=0xaaaaeeee
++CONFIG_DRAM_SUNXI_TPR6=0x44000000
++CONFIG_DRAM_SUNXI_TPR10=0x402f6663
++CONFIG_DRAM_SUNXI_TPR11=0x24242624
++CONFIG_DRAM_SUNXI_TPR12=0x0f0f100f
++CONFIG_MACH_SUN50I_H616=y
++CONFIG_SUNXI_DRAM_H616_LPDDR4=y
++CONFIG_DRAM_CLK=600
++CONFIG_DRAM_ZQ=3881977
++CONFIG_MMC0_CD_PIN="PF6"
++CONFIG_R_I2C_ENABLE=y
++CONFIG_SPL_SPI_SUNXI=y
++CONFIG_CONS_INDEX=1
++CONFIG_BOOTDELAY=5
++CONFIG_SYS_MALLOC_F_LEN=0x4000
++CONFIG_SUPPORT_EMMC_BOOT=y
++CONFIG_AXP313_POWER=y
++CONFIG_AXP_DCDC3_VOLT=1200
++CONFIG_SPL_I2C=y
++CONFIG_SPL_SYS_I2C_LEGACY=y
++CONFIG_SYS_I2C_MVTWSI=y
++CONFIG_SYS_I2C_SLAVE=0x7f
++CONFIG_SYS_I2C_SPEED=400000
++CONFIG_SPI_FLASH_ZBIT=y
++CONFIG_PHY_MOTORCOMM=y
++# CONFIG_SUN8I_EMAC is not set
++CONFIG_SPI=y
++CONFIG_USB_EHCI_HCD=y
++CONFIG_USB_OHCI_HCD=y
++CONFIG_USB_MUSB_GADGET=y
++CONFIG_USB_MUSB_PIO_ONLY=y
++CONFIG_USB_GADGET=y
++CONFIG_USB_GADGET_DOWNLOAD=y
++CONFIG_ARM64_SUPPORT_AARCH32=y
++CONFIG_SYS_CONSOLE_IS_IN_ENV=y
++CONFIG_MMC_SUNXI_SLOT_EXTRA=2
+diff --git a/dts/upstream/src/arm64/allwinner/sun50i-h618-mellow-fly-c5.dts b/dts/upstream/src/arm64/allwinner/sun50i-h618-mellow-fly-c5.dts
+new file mode 100644
+index 00000000000..2eb526b7f2d
+--- /dev/null
++++ b/dts/upstream/src/arm64/allwinner/sun50i-h618-mellow-fly-c5.dts
+@@ -0,0 +1,122 @@
 +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
 +/*
 + * Copyright (C) 2023 Arm Ltd.