configs/ci20_defconfig: bump to kernel 5.4.254

Bump the kernel to the latest release of 5.4 kernel series
to fix an issue with gcc 12.

arch/mips/jz4740/setup.c: In function 'plat_mem_setup':
arch/mips/jz4740/setup.c:64:25: error: comparison between two arrays [-Werror=array-compare]
   64 |         if (__dtb_start != __dtb_end)
      |                         ^~
arch/mips/jz4740/setup.c:64:25: note: use '&__dtb_start[0] != &__dtb_end[0]' to compare the addresses
  CC      fs/debugfs/file.o
cc1: all warnings being treated as errors

Fixed in v5.4.195:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a60def7568216684f62b117c199429c4a9a89570

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/4889436573

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

configs/ci20_defconfig

@@ -15,7 +15,7 @@ BR2_ROOTFS_POST_SCRIPT_ARGS="-c board/ci20/genimage.cfg"
 # kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.4.58"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="5.4.254"
 BR2_LINUX_KERNEL_DEFCONFIG="ci20"
 BR2_LINUX_KERNEL_INSTALL_TARGET=y