arch: arc: Convert to CONFIG_MP_MAX_NUM_CPUS
arch: arc: Convert to CONFIG_MP_MAX_NUM_CPUS

Convert CONFIG_MP_NUM_CPUS to CONFIG_MP_MAX_NUM_CPUS as we work on
phasing out CONFIG_MP_NUM_CPUS.

Signed-off-by: Kumar Gala <a5e5248af4cd4f0ed8c515f61d40a6e2db46a66e@intel.com>

galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr