SPMD: introduce SPMC to SPMD messages

FF-A interface to handle SPMC to SPMD direct messages requests.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Signed-off-by: Max Shvetsov <maksims.svecovs@arm.com>
Change-Id: Ia707a308c55561a31dcfa86e554ea1c9e23f862a
3 files changed