refactor(el3-spmc): avoid unnecessarily revalidating offset

The offset has been validated on the first loop iteration.  Subsequent
iterations can assume it is valid.

Change-Id: Ib06cd0240220b8aa42bcd34c3c40b69d2d86aa72
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
1 file changed