V4L/DVB (11278): bttv: convert to v4l2_subdev since i2c autoprobing will disappear.

Since i2c autoprobing will disappear bttv needs to be converted to use
v4l2_subdev instead.

Without autoprobing the autoload module option has become obsolete. A warning
is generated if it is set, but it is otherwise ignored.

Since the bttv card definitions are of questionable value a new option was
introduced to allow the user to control which audio module is selected:
msp3400, tda7432 or tvaudio (or none at all).

By default bttv will use the card definitions and fallback on tvaudio as the
last resort.

If no audio device was found a warning is printed.

The saa6588 RDS device is now also explicitly probed since it is no longer
possible to autoprobe it. A new saa6588 module option was added to override
the card definition since I suspect more cards have this device than one
would guess from the card definitions.

Note that the probe addresses of the i2c modules are hardcoded in this
driver. Once all v4l drivers are converted to v4l2_subdev this will be
cleaned up. Such data belongs in an i2c driver header.

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