dri-devel mailing list moved - update MAINTAINERS

dri-devel mailing list moved - update MAINTAINERS

I posted to dri-devel@lists.sourceforge.net, and got a bounce back:

   The dri-devel list has moved to freedesktop.org (see
   http://lists.freedesktop.org/mailman/listinfo/dri-devel). If you were
   subscribed to the list here, the subscription should have been
   transferred to the new location.

   Please only post to the new list.

Fix MAINTAINERS to correspond.

Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>