HDMI and DisplayPort both support IT Content Type information that
tells the receiver what type of material the video is, graphics such
as from a PC desktop, Photo, Cinema or Game (low-latency).

This patch adds controls for receivers and transmitters to get/set
this information.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>