Add a function to the CameraSensor class that allows to test a format without applying it to the subdevice and without modifying any control value associated with the camera sensor. Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>