arch: arm: mpu: remove arm_core_mpu_enable/disable internal API

arm_core_mpu_enable() and arm_core_mpu_disable() functions are
effectively static functions, only used in the drivers for ARM
and NXP MPU, therefore, we do not need to expose them in the
arm_core_mpu_dev.h header.

Signed-off-by: Ioannis Glaropoulos <[email protected]>

Author: ioannisg

arch/arm/core/cortex_m/mpu/arm_core_mpu_dev.h

@@ -106,16 +106,6 @@ struct k_thread;
  * ARM_MPU support.
  */
 
-/**
- * @brief enable the MPU
- */
-void arm_core_mpu_enable(void);
-
-/**
- * @brief disable the MPU
- */
-void arm_core_mpu_disable(void);
-
 /**
  * @brief configure a set of fixed (static) MPU regions
  *