V4L/DVB (13553): v4l: Use the video_is_registered function in device drivers

Fix all device drivers to use the video_is_registered function instead
of checking video_device::minor.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/stradis.c b/drivers/media/video/stradis.c
index eaada39..c890905 100644
--- a/drivers/media/video/stradis.c
+++ b/drivers/media/video/stradis.c
@@ -2134,7 +2134,7 @@
 	free_irq(saa->irq, saa);
 	if (saa->saa7146_mem)
 		iounmap(saa->saa7146_mem);
-	if (saa->video_dev.minor != -1)
+	if (video_is_registered(&saa->video_dev))
 		video_unregister_device(&saa->video_dev);
 }