SPM: SGI: Map memory allocated for secure partitions

The secure partition manager reserves chunks of memory which are used
for the S-EL0 StandaloneMM image and the buffers required for
communication between the Non-Secure world with the StandaloneMM
image. Add the memory chunks to relevant arrays for mapping the
regions of memory with corresponding attributes.

Change-Id: If371d1afee0a50ca7cacd55e16aeaca949d5062b
Signed-off-by: Sughosh Ganu <sughosh.ganu@arm.com>