arm: cmsis: Introduce CMSIS layer

Support using CMSIS defines and functions, we either pull the expect
defines/enum from the SoC HAL layers via <soc.h> for the SoC or we
provide a default set based on __NVIC_PRIO_BITS is defined.

We provide defaults in the case for:
	IRQn_Type enum
	*_REV define (set to 0)
	__MPU_PRESENT define (set to 0 - no MPU)
	__NVIC_PRIO_BITS define (set to CONFIG_NUM_IRQ_PRIO_BITS)
	__Vendor_SysTickConfig (set to 0 - standard SysTick)

Jira: ZEP-1568

Change-Id: Ibc203de79f4697b14849b69c0e8c5c43677b5c6e
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>