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/s2255drv.c b/drivers/media/video/s2255drv.c
index 41765f3..4201abc 100644
--- a/drivers/media/video/s2255drv.c
+++ b/drivers/media/video/s2255drv.c
@@ -1880,7 +1880,7 @@
 
 	int i;
 	for (i = 0; i < MAX_CHANNELS; i++) {
-		if (-1 != dev->vdev[i]->minor) {
+		if (video_is_registered(dev->vdev[i])) {
 			video_unregister_device(dev->vdev[i]);
 			printk(KERN_INFO "s2255 unregistered\n");
 		} else {