[media] gspca_kinect: add support for the depth stream

Add support for the depth stream at 10bpp, for now use a 'depth_mode'
command line parameter to switch between video and depth mode.

Signed-off-by: Alexander Sosna <alexander@xxor.de>
Signed-off-by: Antonio Ospite <ao2@ao2.it>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>