Implement basic auto-exposure (AE) and auto-gain (AG) correction functions. The functions computeTargetExposure() and computeGain() are adapted from the Raspberry Pi AGC implementation to suit the IPU3 structures, and filtering is added to reduce visible stepsize when there are large exposure changes. Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Tested-by: Jacopo Mondi <jacopo@jmondi.org> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>