media: vivid: add display present control

Add a custom control for selecting the presence of a display connected
to the active output. This control is part of an effort to implement
proper HDMI (dis)connect behavior for vivid.

Signed-off-by: Johan Korsnes <johan.korsnes@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>