media: imx: imx7_mipi_csis: Update MAINTAINERS

Given my recent contributions to the imx7-mipi-csis driver, I can as
well be listed as a maintainer.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

MAINTAINERS

@@ -11283,6 +11283,7 @@ F:	include/media/imx.h
 
 MEDIA DRIVERS FOR FREESCALE IMX7
 M:	Rui Miguel Silva <rmfrfs@gmail.com>
+M:	Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 L:	linux-media@vger.kernel.org
 S:	Maintained
 T:	git git://linuxtv.org/media_tree.git