Now that the IPU3's Agc is derived from MeanLuminanceAgc we can delete all the unecessary bespoke functions. Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com> Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>