SCMI Comms: Add secure test suite

Adds support for local testing of the SCMI comms partition using the
TFM_TIMER0 interrupt to exercise the partition's interrupt handler.

Signed-off-by: Jamie Fox <jamie.fox@arm.com>
Change-Id: I21c7f9c93f4f057984a290f415888326df7dce71
8 files changed