arch: arm: beetle: Pull in CMSDK header for CMSIS support on Beetle

Pulled CMSDK_BEETLE.h from mbed-os as a starting point to enable CMSIS
support on Beetle.  Trimed the file down that what we need on Zephyr
(dropped Device Specific Peripheral Section and system_CMSDK_BEETLE.h).

This lets us drop soc_mpu.h which duplicates MPU info that is defined in
CMSIS headers.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>