arch: arm: no special case for MPUs with power-of-2-align requirement
arch: arm: no special case for MPUs with power-of-2-align requirement

Field stack_info.size is supposed to hold the actual writable
thread stack area, above what is pointed to by stack_info.start.
Therefore, in all MPU architectures we can program the Thread
Stack MPU region as starting from thread->stack_obj and with
size equal to stack_info.size plus the (possible) difference
between stack_obj and stack_info.start.

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

zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,ldts/zephyr,ldts/zephyr,ldts/zephyr,galak/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,ldts/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,finikorg/zephyr