[media] media drivers: annotate fall-through

Avoid warnings like those:

drivers/media/pci/ddbridge/ddbridge-core.c: In function 'dvb_input_detach':
drivers/media/pci/ddbridge/ddbridge-core.c:787:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
   if (input->fe) {
      ^
drivers/media/pci/ddbridge/ddbridge-core.c:792:2: note: here
  case 4:
  ^~~~
...

On several cases, it is just that gcc 7.1 is not capable of
understanding the comment, but on other places, we need an
annotation.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/uvc/uvc_video.c

@@ -1327,7 +1327,7 @@ static void uvc_video_complete(struct urb *urb)
 	case -ENOENT:		/* usb_kill_urb() called. */
 		if (stream->frozen)
 			return;
-
+		/* fall through */
 	case -ECONNRESET:	/* usb_unlink_urb() called. */
 	case -ESHUTDOWN:	/* The endpoint is being disabled. */
 		uvc_queue_cancel(queue, urb->status == -ESHUTDOWN);