kernel: bump 6.18 to 6.18.38

kernel: bump 6.18 to 6.18.38

Changelog: https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.18.38

Removed upstreamed:
  linux/generic/backport-6.18/300-v7.2-MIPS-smp-report-dying-CPU-to-RCU-in-stop_this_cpu.patch[1]

All other patches automatically rebased via update_kernel.sh

1. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.18.38&id=f9b57a0015c241274651f4b36627f56b1b5a8651

Build system: x86/64
Build-tested: x86/64-glibc
Run-tested: x86/64-glibc

Signed-off-by: John Audia <therealgraysky@proton.me>
Link: https://github.com/openwrt/openwrt/pull/24083
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>