[media] cx23885: Add ALSA support

[stoth@kernellabs.com: add it to the makefile and fix snd_card binding]
[liplianin@netup.ru: videobuf: Remove the videobuf_sg_dma_map/unmap functions]

Signed-off-by: Mijhail Moreyra <mijhail.moreyra@gmail.com>
Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Igor M. Liplianin <liplianin@netup.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>