soc: arm: mps2: Add configuration for CMSDK Driver

This patch adds the configuration parametes required to enable CMSDK
(Cortex-M System Design Kit) Drivers at MPS2 soc level.

It provides as well the definitions for the MPS2 System Control
registers.

Change-Id: I06181dcfeb4fb887425b85ec9a99c268c857a34e
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@linaro.org>