fix(el3-spmc): fix incorrect CASSERT

Check that the size of desc->emad_count is 4, not that sizeof(int) is
nonzero.  Also improve a comment.

Change-Id: I8bf69b637158ddffe2d08aed3d9879a4d7fd3514
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
1 file changed