feat(ff-a): forward FFA_VERSION from SPMD to SPMC

feat(ff-a): forward FFA_VERSION from SPMD to SPMC

Introduced by FF-A v1.1 we must forward a call to FFA_VERSION
to the SPMC so that the ffa version of the caller can be stored
for later use. Since the return of FFA_VERSION is not wrapped in
a FF-A call we need to  use a direct message request to do this
forwarding. For the spmd_handler in the SPMC to hand off to the
correct function we use w2 to specify a target framework function.
Therefore we must update PSCI CPU_OFF to do this as well.

Change-Id: Ibaa6832b66f1597b3d65aa8986034f0c5916016d
Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>