refactor(el3-spmc): check emad_count offset

Subsequent code will assume that it version-independent, so check it
with a CASSERT.

Change-Id: I233b51ef700103f1a0789d5608e3b02c96d0eeb7
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
1 file changed