V4L/DVB (3253): Add V4L2 commands to tvaudio

- debug messages changed to be like the other modules
- Add V4L2 commands VIDIOC_S_TUNER, VIDIOC_G_TUNER,
VIDIOC_S_STD and VIDIOC_S_FREQUENCY.

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