For the implementation of a manual colour temperature setting, it is necessary to read predefined colour gains per colour temperature from the tuning file. Implement this in a backwards compatible way. If no gains are contained in the tuning file, loading just continues as before. Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>