V4L/DVB (8788): v4l: replace video_get_drvdata(video_devdata(filp)) with video_drvdata(filp)

Use the new video_drvdata(filp) function where it is safe to do so.

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