fix(spmd): fix FFA_VERSION forwarding

When FFA_VERSION is forwarded from SPMD to SPMC, ensure that the full
NS GP regs context incl. x8-x17 is carried when building the SPMD to
SPMC direct message.

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I3467c0e04de95ab80f7c86a0763021a5fa961e4d
2 files changed