[media] gspca - kinect: fix comments referring to color camera

Use the expression "video stream" instead of "color camera" which is
more correct as the driver supports the RGB and IR image on the same
endpoint.

Signed-off-by: Antonio Ospite <ospite@studenti.unina.it>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>