arch: arc: apply STACK_GUARD_SIZE and optimize the mpu driver

* apply STACK_GUARD_SIZE, no extra space will be added if
  MPU_STACK_GUARD is disabled
* When ARC_STACK_CHECKING is enabled, MPU_STACK_GUARD will be
  disabled
* add two new api: arc_core_mpu_default and arc_core_mpu_region
  to configure mpu regions
* improve arc_core_mpu_enable and arc_core_mpu_disable

Signed-off-by: Wayne Ren <wei.ren@synopsys.com>