MAINTAINERS: add SPI co-maintainer.

Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NAndrew Morton <akpm@linux-foundation.org>

MAINTAINERS

@@ -4937,6 +4937,7 @@ F:	drivers/char/specialix*
 
 SPI SUBSYSTEM
 M:	David Brownell <dbrownell@users.sourceforge.net>
+M:	Grant Likely <grant.likely@secretlab.ca>
 L:	spi-devel-general@lists.sourceforge.net
 S:	Maintained
 F:	Documentation/spi/