[media] v4l2-ctrls: add new controls for MPEG decoder devices

As discussed during the 2011 V4L-DVB workshop we want to create a proper V4L2
decoder API that replaces the DVBv5 API that has been used until now.

This adds the four controls necessary to be able to switch ivtv over to this
new API.

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