Fix MOVSXD mem to reference 16/32b. Update historical comment.
Fix MOVSXD mem to reference 16/32b. Update historical comment.

  * Tested Penryn, NHM and WSM. My Merom/Penryn were offline.

Change-Id: I4f00f41434480ed5a555460bff23e3af7ec38477
(cherry picked from commit d1d83a249795b7f46eb6834af7f4e72e2388fb84)

intelxed/xed,intelxed/xed,intelxed/xed,intelxed/xed