arm: userspace: fix initial user sp location
arm: userspace: fix initial user sp location

The initial user stack pointer gets rounded to STACK_ALIGN_SIZE,
which can be much finer granularity than MPU regions. With
certain stack size values passed to k_thread_create(), the stack
pointer can be set past the defined region for the user thread's
stack, causing an immediate MPU fault.

Signed-off-by: Andrew Boie <aab045b28152628be6af0e556050d0381fd0a34d@intel.com>

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