V4L/DVB (3588): Remove VIDIOC_G/S_AUDOUT from msp3400

VIDIOC_G/S_AUDOUT does not belong in msp3400 (it's a user level command,
not to be used in internal i2c drivers). Also fix a compile warning and
improve LOG_STATUS.

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