Add a caps() function that exposes the V4L2 capabilities for the device. This is useful for generic code that can't hardcode any a priori knowledge of the device, such as in a simple pipeline handler. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>