V4L/DVB (6052): ivtv: fix udma yuv bug

Using udma yuv causes the driver becomes locked into that mode. This prevents
use of the mpeg decoder & non-udma yuv output. This patch clears the
operating mode when the device is closed.

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>