[media] DocBook/video.xml: Document the remaining data structures

Now, all data structures are commented. A few ioctls remain undocumented:

Error: no ID for constraint linkend: VIDEO_GET_SIZE.
Error: no ID for constraint linkend: VIDEO_GET_FRAME_RATE.
Error: no ID for constraint linkend: VIDEO_GET_PTS.
Error: no ID for constraint linkend: VIDEO_GET_FRAME_COUNT.
Error: no ID for constraint linkend: VIDEO_COMMAND.
Error: no ID for constraint linkend: VIDEO_TRY_COMMAND.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>