Change the name of type ffa_vm_id_t

The type ffa_vm_id_t is used for all ffa_id variables not just
ones specific to vms so remove this element from the name to make
it simple ffa_id_t

Signed-off-by: Daniel Boulby <daniel.boulby@arm.com>
Change-Id: I29d751880c29b0a401cbc698f856c3651cc02789
12 files changed