Add two new media entity function definitions for video multiplexers
and video interface bridges.

- renamed MEDIA_ENT_F_MUX to MEDIA_ENT_F_VID_MUX
Signed-off-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: NSteve Longerbeam <steve_longerbeam@mentor.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>