[media] uvcvideo: Add quirk to force the Oculus DK2 IR tracker to grayscale

This patch adds a quirk to force Y8 pixel format even if the camera reports
half-width YUYV.

Signed-off-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>