arch: arm64: add GIC ICC system register accessors
arch: arm64: add GIC ICC system register accessors

-Add GIC system register defines.
-Add sysreg read write macros.

Signed-off-by: Sandeep Tripathy <00bfda8ff3a1761c3b14f4a98fd430fff51876de@broadcom.com>

Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr