arch: arm64: mpu: remove unnecessary include

<soc.h> was not required.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

arch/arm64/core/cortex_r/arm_mpu.c

@@ -9,7 +9,6 @@
 #include <zephyr/init.h>
 #include <zephyr/kernel.h>
 #include <kernel_arch_func.h>
-#include <soc.h>
 #include <zephyr/arch/arm64/mm.h>
 #include <zephyr/linker/linker-defs.h>
 #include <zephyr/logging/log.h>