[media] ivtv: mark DVB "borrowed" ioctls as deprecated

changeset da8ec560 ("[media] ivtv: implement new decoder command
ioctls") implemented proper support for mpeg audio and video control
at V4L2 API. Since then, the usage of the the DVB APIs is deprecated.

However, we never actually marked it as deprecated nor provided any
way to disable it. Let's do it now.

This patch prepares for the removal of this bad usage on a couple
of Kernel versions.

Fixes: da8ec560

 ("[media] ivtv: implement new decoder command ioctls")

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