V4L/DVB (10755): cx18: Convert the integrated A/V decoder core interface to a v4l2_subdev

This is the next step in converting the cx18 driver to use the v4l2_device/
v4l2_subdevice framework.  This is a straightforward conversion of the
cx18_av_*[ch] files.  It compiles, but leaves the driver in an unlinkable
state at the moment.

Note, the cx18 integrated A/V digitizer will now make a host match at address 1,
as far as v4l2-dbg is concerned.  That means it identifies itself as a separate
"chip", and acts as an alias to the integrated A/V decoder registers that are
also available with the host match at address 0.

Signed-off-by: Andy Walls <awalls@radix.net>
[mchehab@redhat.com: fix merge conflicts due to the removal of v4l2_ctrl_query_fill_std()]
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>