V4L/DVB (6716): ivtv: yuv interlace mode change

Interlace mode selection code moved into the frame setup phase, so it's now
run before the frame is loaded into a hardware buffer. Given that it can
affect how a new frame is displayed, it was a bit stupid running it after the
frame was already visible.

A few stray interlace related variables which were linked to individual frames
have now been moved into the yuv_frame_info struct. This means that all
variables linked to a specific frame are in the same place & not scattered.

Minor code reformatting in areas touched by the above changes.

Signed-off-by: Ian Armstrong <ian@iarmst.demon.co.uk>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>