V4L/DVB (4548): Better temporal filter handling.

Adjust temporal filter if necessary. The problem with the temporal
filter is that it works well with full resolution capturing, but
not when the capture window is scaled (the filter introduces
a ghosting effect). So if the capture window changed, and there is
no updated filter value, then the filter is set depending on whether
the new window is full resolution or not.
For full resolution a setting of 8 really improves the video
quality, especially if the original video quality is suboptimal. 
Also report VBI Format in VIDIOC_LOG_STATUS, it was missing.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>