Collect subdev capabilities at open() time. Model the V4L2SubdevCapabilties as V4L2Capability from the video device class. Signed-off-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Tested-by: Jacopo Mondi <jacopo@jmondi.org> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>