[media] ivtv, ivtv-alsa: Add initial ivtv-alsa interface driver for ivtv

This is a cut-and-paste port of the cx18-alsa driver to
create an ivtv-alsa interface module for the ivtv driver.
It is not actually hooked-up to the PCM stream DMA buffers
from the ivtv driver yet.  That will be done in a coming change,
since that portion is so very different from the cx18 driver.
This code has all or more of the bugs and shortcomings of the
cx18-alsa interface driver: inconsistent use of itvsc->slock,
ivtv-alsa-mixer.c is dead code, assumes 48 ksps regardless
of the actual setting of the audio capture, problems with
proper struct ivtv and struct ivtv_stream housekeeping,
struct ivtv_open_id.v4l2_fh abuse, and $DIETY knows what else.

Signed-off-by: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>