[media] usbtv: Add driver for Fushicai USBTV007 video frame grabber

Reverse-engineered driver for cheapo video digitizer, made from observations of
Windows XP driver. The protocol is not yet completely understood, so far we
don't provide any controls, only support a single format out of three and don't
support the audio device.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-media@vger.kernel.org