media: uvcvideo: Drop the uvc_driver structure

The uvc_driver structure used to contain more fields, but those got
removed in commit ba2fa996 ("[media] uvcvideo: Hardcode the
index/selector relationship for XU controls"). The structure is now just
a wrapper around usb_driver. Drop it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>