Platform: Rename SST to PS for FVP_SSE300_MPS2

Updates FVP_SSE300_MPS2 platform files to use PS names instead of SST.

Change-Id: I428668a645cb0c47b6f5b62ab9a0fc61e116c2fc
Signed-off-by: Jamie Fox <jamie.fox@arm.com>
2 files changed