V4L/DVB (9190): ivtv: yuv write() error handling tweak

Modifies behaviour of a failed dma write() operation for the yuv device.
If the dma transfer for the yuv device fails, the write() operation will now
exit immediately.

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@redhat.com>