feat(spm): add FFA_MSG_SEND2 forwarding in SPMD

Add FF-A v1.1 indirect messaging ABI FFA_MSG_SEND2 to SPMD to allow
message forwarding across normal/secure worlds.

Change-Id: I074fbd2e4d13893925f987cee271d49da3aaf64b
Signed-off-by: Federico Recanati <federico.recanati@arm.com>
2 files changed