feat(mpam): add MPAM system registers access test

Added a test which reads MPAM system registers to ensure that
EL3 is giving permission to Non-secure EL2 to access these registers.

Change-Id: Ie701a19c9682df6d6aeaec086954e275afff1843
Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
6 files changed