configs/freescale_p1025twr: bump linux kernel to 6.12.27

Since commit [1] "package/binutils: make 2.43 the default version",
the freescale_p1025twr_defconfig fails to build the Linux
kernel, with the error:

    arch/powerpc/boot/util.S: Assembler messages:
    arch/powerpc/boot/util.S:49: Error: junk at end of line, first unrecognized character is `0'
    arch/powerpc/boot/util.S:54: Error: syntax error; found `b', expected `,'
    arch/powerpc/boot/util.S:54: Error: junk at end of line: `b'

This commit fixes the issue by updating the Linux kernel to the latest
LTS version.

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/9967089759

[1] https://gitlab.com/buildroot.org/buildroot/-/commit/360fd01de20eb42aa0e6b5e9f7b37eaa104c6fc9

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/freescale_p1025twr_defconfig

@@ -1,10 +1,10 @@
 BR2_powerpc=y
 BR2_powerpc_8548=y
-BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_15=y
+BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_12=y
 BR2_TARGET_GENERIC_GETTY_PORT="ttyS0"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.15.7"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.12.27"
 BR2_LINUX_KERNEL_DEFCONFIG="mpc85xx_smp"
 BR2_LINUX_KERNEL_DTS_SUPPORT=y
 BR2_LINUX_KERNEL_INTREE_DTS_NAME="fsl/p1025twr"