Kernel: T9195: Update Linux Kernel to 6.18.44

Upgrade rolling release Kernel version.

This is not a routine bump: 6.18.39 through 6.18.41 are unbootable on Intel
Denverton (DNV), Ice Lake Xeon D (ICX-D/CDF) and Snowridge (SNR) platforms,
which covers a large part of the small-form-factor hardware VyOS is deployed
on. We moved to 6.18.41 in 97c2a87 (T9067).

Upstream b1b4efea05a5 ("serial: 8250_mid: Disable DMA for selected platforms",
in stable since v6.18.39) set dnv_board.setup and dnv_board.exit to
PTR_IF(false, ...) to work around a DMA errata, but left the three call sites
in mid8250_probe() and mid8250_remove() dereferencing them unguarded. Since
CONFIG_SERIAL_8250_MID=y in our defconfig, the driver is built in and the
resulting NULL function pointer call happens during early PCI probe, killing
the probing kworker with interrupts disabled and wedging the boot:

  CPU: 0 UID: 0 PID: 11 Comm: kworker/0:1 Not tainted 6.18.41-vyos #1
  Hardware name: Supermicro SYS-510D-10C-FN6P/X12SDV-10C-SP6F, BIOS 2.2a
  Workqueue: events work_for_cpu_fn
  RIP: 0010:0x0
  Call Trace:
   mid8250_probe.part.0+0x10c/0x230
   local_pci_probe+0x41/0x90
   work_for_cpu_fn+0x16/0x20
  note: kworker/0:1[11] exited with irqs disabled

The missing NULL checks were added by 7fb13fd7e9a5 ("serial: 8250_mid: Fix
NULL function pointer dereference on DNV/ICX-D/SNR platforms"), which is in
stable as of v6.18.42, so any release from .42 onwards resolves this. Taking
.44 as the current 6.18.y tip.

All five patches under patches/kernel/ still apply: of the files they touch,
only net/ipv6/route.c saw upstream changes in this range (1db34097998c, in
__ip6_del_rt_siblings() around line 4011), which does not overlap the
rt6_link_filter()/rt6_score_route() hunks of 0001 around line 717.

Changelogs:
* 6.18.44 https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.18.44
* 6.18.43 https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.18.43
* 6.18.42 https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.18.42

Author: statio

data/defaults.toml

@@ -14,7 +14,7 @@ vyos_mirror = "https://packages.vyos.net/repositories/rolling"
 vyos_branch = "rolling"
 release_train = "rolling"
 
-kernel_version = "6.18.41"
+kernel_version = "6.18.44"
 kernel_flavor = "vyos"
 bootloaders = "syslinux,grub-efi"