soc: arm: nxp: ensure code cache is enabled at boot for RT11xx

Ensure code cache is enabled at boot for RT11xx. CMSIS SystemInit should
enable the code cache, but if CONFIG_INIT_ARCH_HW_AT_BOOT=y and
CONFIG_CACHE_MANAGEMENT=y, then the cache will be disabled after
SystemInit is called. Since calling SCB_EnableICache will not
change hardware settings if the ICACHE is already enabled, just
call it unconditionally during init.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>