V4L/DVB (11297): cx23885: convert to v4l2_subdev.

Convert this driver to v4l2_subdev. Note that currently the only card with
analog support in this driver is the HVR-1800. The analog tuner support in
this driver is limited to what is needed for this board. When analog support
is added for other cards, then the tuner load code will probably have to be
expanded to take care of those boards. For example, there is currently no
support for either radio tuners or tda9887 demods.

I'd like to thank Steven Toth for testing this on his HVR-1800.

Tested-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>