V4L (1023): Added Hauppauge ImpactVCB board

- Modifications to bttv to support the Hauppauge ImpactVCB product
(Model #64900).

Signed-off-by: Steven Toth <stoth@hauppauge.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>