ARM: shmobile: defconfig: Supplement DTB with ATAG information

Enable CONFIG_ARM_ATAG_DTB_COMPAT to allow U-Boot to override kernel
command line from DTB using the bootargs argument.  This is needed at
least on R-Car H1 Marzen to control the command line from U-Boot.

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/20250116153204.615736-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Author: Niklas Söderlund

arch/arm/configs/shmobile_defconfig

@@ -14,6 +14,7 @@ CONFIG_SCHED_MC=y
 CONFIG_NR_CPUS=8
 CONFIG_HIGHMEM=y
 CONFIG_ARM_APPENDED_DTB=y
+CONFIG_ARM_ATAG_DTB_COMPAT=y
 CONFIG_CPU_FREQ=y
 CONFIG_CPU_FREQ_STAT=y
 CONFIG_CPU_FREQ_GOV_POWERSAVE=y