arch: arm: use stored value for MMFAR
arch: arm: use stored value for MMFAR

Make MPU stack guard checks use the previously stored value
of the MemManage Fault Address Register, to ensure that the
address-under-check is valid.

Signed-off-by: Ioannis Glaropoulos <5921cc8bab7e1d4329f52fd8f6268f9692e3de80@nordicsemi.no>

Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,kraj/zephyr,zephyriot/zephyr,ldts/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,punitvara/zephyr,nashif/zephyr,Vudentz/zephyr,ldts/zephyr,explora26/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,mbolivar/zephyr,punitvara/zephyr,ldts/zephyr,Vudentz/zephyr,zephyriot/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,kraj/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,kraj/zephyr,galak/zephyr,nashif/zephyr,zephyriot/zephyr,kraj/zephyr,mbolivar/zephyr,mbolivar/zephyr,punitvara/zephyr,mbolivar/zephyr,finikorg/zephyr,explora26/zephyr,finikorg/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,zephyriot/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr,kraj/zephyr,ldts/zephyr,explora26/zephyr,nashif/zephyr,punitvara/zephyr,zephyriot/zephyr