Add the missing `override` specifiers in the derived classes of `Debayer`, so that the compiler can ensure that the functions in the derived classes really override the functions in the base class. Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Bryan O'Donoghue <bod.linux@nxsw.ie>