Add the V4L2_CID_EXPOSURE control to the list of mandatory controls the sensor driver has to report and document this new requirement. While at it, re-sort the mandatory V4L2 controls in alphabetical order in the CameraSensor class and remove the above comment as the usage of the controls is better reported in the documentation. Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>