configs/imx23evk: bump Linux and U-Boot

The imx23evk_defconfig fail to build the Kernel with message:

    arch/arm/mm/proc-arm926.S: Assembler messages:
    arch/arm/mm/proc-arm926.S:477: Error: junk at end of line, first unrecognized character is '#'

The upstream fix is [1] introduced in Kernel v5.5.

This commit fixes this issue by updating the Kernel. While at it,
U-Boot is also updated. The Kernel DTS name is also updated, to follow
the reorganization in [2], first included in v6.5.

Fixes:
- https://gitlab.com/buildroot.org/buildroot/-/jobs/6338079204

[1] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=790756c7e0229dedc83bf058ac69633045b1000e
[2] https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=724ba6751532055db75992fc6ae21c3e322e94a7

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Romain Naour <romain.naour@smile.fr>

configs/imx23evk_defconfig

@@ -2,8 +2,8 @@
 BR2_arm=y
 BR2_arm926t=y
 
-# Linux headers same as kernel, a 4.8 series
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_8=y
+# Linux headers same as kernel, a 6.6 series
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_6=y
 
 # system
 BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
@@ -11,16 +11,16 @@ BR2_TARGET_GENERIC_GETTY_PORT="ttyAMA0"
 # kernel
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.8.6"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.6.21"
 BR2_LINUX_KERNEL_DEFCONFIG="mxs"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
-BR2_LINUX_KERNEL_INTREE_DTS_NAME="imx23-evk"
+BR2_LINUX_KERNEL_INTREE_DTS_NAME="nxp/mxs/imx23-evk"
 
 # bootloader
 BR2_TARGET_UBOOT=y
 BR2_TARGET_UBOOT_BOARDNAME="mx23evk"
 BR2_TARGET_UBOOT_CUSTOM_VERSION=y
-BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2021.10"
+BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2024.01"
 BR2_TARGET_UBOOT_FORMAT_SD=y
 
 # Filesystem