efifb: Add override for 11" Macbook Air 3,1

The 11" Macbook Air appears to claim that its stride is 1366, when it's
actually 2048. Override it.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>