[media] v4l2 core: add the missing pieces to support DVI/HDMI/DisplayPort

These new controls and two new ioctls make it possible to properly support
VGA, DVI-A/D/I, HDMI and DisplayPort connectors. All these controls and the
ioctls are all at the sub-device level. They are meant for V4L2 bridge/platform
drivers or to be accessed on embedded systems through /dev/v4l-subdev* device
nodes.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>