Don't call suspend/resume functions if they have not been
defined.
Signed-off-by: NRobert Jarzmik <rjarzmik@free.fr>
Acked-By: NJörn Engel <joern@logfs.org>
Signed-off-by: NUwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>