MAINTAINERS: Update media entries

Now that we've created a /drivers/staging/media, put it together with
/drivers/media. Also, added there a missing entry for the Media API spec.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index e839b95..273b049 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4234,7 +4234,9 @@
 S:	Maintained
 F:	Documentation/dvb/
 F:	Documentation/video4linux/
+F:	Documentation/DocBook/media/
 F:	drivers/media/
+F:	drivers/staging/media/
 F:	include/media/
 F:	include/linux/dvb/
 F:	include/linux/videodev*.h