arch: arm: mpu: functionality to configure static memory regions (v8)

This commit contains the added functionality to program the
ARM8-M MPU, so it can configure the static memory regions at
boot time, as well as mark the areas, inside which dynamic MPU
region configuration at run-time will be allowed.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>