[media] v4l: Update subdev-formats doc with new MEDIA_BUS_FMT values

In order to have subsytem agnostic media bus format definitions we've
moved media bus definition to include/uapi/linux/media-bus-format.h and
prefixed them with MEDIA_BUS_FMT instead of V4L2_MBUS_FMT.

Update the v4l documentation accordingly.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>