[media] uvcvideo: Fix empty packet statistic

The frame counters are inadvertently counting packets with content as
empty.

Fix it by correcting the logic expression

Fixes: 7bc5edb0 [media] uvcvideo: Extract video stream statistics
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/uvc/uvc_video.c

@@ -818,7 +818,7 @@ static void uvc_video_stats_decode(struct uvc_streaming *stream,
 
 	/* Update the packets counters. */
 	stream->stats.frame.nb_packets++;
-	if (len > header_size)
+	if (len <= header_size)
 		stream->stats.frame.nb_empty++;
 
 	if (data[1] & UVC_STREAM_ERR)