gma500: move the ASLE enable

Otherwise we end up getting the masks wrong, can get events before we
are doing power control and other ungood things.  Again this is a
regression fix where the ordering of handling was disturbed by other
work, and the user experience on some boxes is a blank screen.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>