MAINTAINERS: update Laurent Pinchart email

Laurent is sending auto-replies with a new email address, so might as well
update MAINTAINERS.

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>