drm/udl: Fixed problem with UDL adpater reconnection

Fixed problem with DisplayLink and DisplayLink certified adapers in drm/udl
driver when adapter doesn't want to work if it was initialized with
disconnected DVI cable by enabling drm connectot polling and updating
current connector's state.

Signed-off-by: Robert Tarasov <tutankhamen@chromium.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013001350.172155-1-tutankhamen@chromium.org
diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
index 31421b6..3c45a30 100644
--- a/drivers/gpu/drm/udl/udl_drv.c
+++ b/drivers/gpu/drm/udl/udl_drv.c
@@ -14,6 +14,9 @@
 static int udl_usb_suspend(struct usb_interface *interface,
 			   pm_message_t message)
 {
+	struct drm_device *dev = usb_get_intfdata(interface);
+
+	drm_kms_helper_poll_disable(dev);
 	return 0;
 }
 
@@ -21,6 +24,7 @@ static int udl_usb_resume(struct usb_interface *interface)
 {
 	struct drm_device *dev = usb_get_intfdata(interface);
 
+	drm_kms_helper_poll_enable(dev);
 	udl_modeset_restore(dev);
 	return 0;
 }