V4L/DVB (11053): saa7134: set v4l2_dev field of video_device

The v4l2_dev field of video_device wasn't initialized. The parent field
is derived from v4l2_dev, so that doesn't need to be set anymore.

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