[media] videodev2.h: add VICs and picture aspect ratio

Add picture aspect ratio information, the CEA-861 VIC (Video Identification
Code) and the HDMI VIC to struct v4l2_bt_timings.

The picture aspect was chosen rather than the pixel aspect since 1) the
CEA-861 standard uses picture aspect, and 2) pixel aspect ratio can become
tricky when dealing with pixel repeat timings. While we don't support those
yet at the moment, this might become necessary. And in that case using
picture aspect ratio makes more sense. And converting picture aspect ratio
to pixel aspect ratio is easy enough.

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