drm/udl: Switch to atomic suspend/resume helpers

We can use the generic suspend/resume helpers for atomic modesetting.
Switch udl over.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210084905.5570-4-tzimmermann@suse.de

drivers/gpu/drm/udl/udl_drv.h

@@ -72,7 +72,6 @@ struct udl_device {
 
 /* modeset */
 int udl_modeset_init(struct drm_device *dev);
-void udl_modeset_restore(struct drm_device *dev);
 void udl_modeset_cleanup(struct drm_device *dev);
 struct drm_connector *udl_connector_init(struct drm_device *dev);