Add hardware-verified V536 (0x1816) UART support and fix thunk_addr

[akalime]

bare-metal: Add hardware-verified V536 (0x1816) support

Add V536 to bare-metal.c SoC table and correct thunk_addr in soc_info.c.

bare-metal.c: Add V536 (0x1816) entry with UART0 at 0x05000000 on
SUNXI_GPH(9) MUX_5, verified on Eonon T86PRO_V101 hardware by reading
live UART struct from SRAM via sunxi-fel.

soc_info.c: Correct V536 thunk_addr from 0x2A200 to 0x2E000. Upstream
value was copied from V831 without hardware verification. 0x2E000
confirmed working on real V536 silicon.

Closes #148

[akalime]

Tested on real Allwinner V536 hardware (Eonon T86PRO_V101 dashcam).
soc_id 0x1816 confirmed via sunxi-fel version output.

Key difference from previous attempt (Dec 2021): that PR was tested on
a V316 with assumed V536 compatibility. This PR corrects thunk_addr to
0x2E000, verified working on actual V536 silicon via FEL sessions.
UART base 0x05000000 confirmed from kernel boot log and live SRAM read.
Watchdog at 0x030090a0 confirmed from kernel boot log.
sid_base 0x03006000 confirmed from device tree.

[akalime]

$ sudo ./sunxi-fel version
AWUSBFEX soc=00001816(V536) 00000001 ver=0001 44 08 scratchpad=00027e00

uart0: ttyS0 at MMIO 0x5000000

sunxi-wdt 30090a0.watchdog: Watchdog enabled (timeout=16 sec, nowayout=0)

sunxi-sid@03006000