msm: smem: add mpu based security support

Add support for the Memory Protection Unit (MPU) based shared memory
security feature.  This feature fragments shared memory into multiple
partitions and restricts access for each partition to a limited set of
processors which is enforced by MPUs.

Change-Id: I0878e1df3aad5aab49b845918be095c71956029d
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>