[media] av7110: potential divide by zero

"len" comes from dvb_video_ioctl() and there is a possibility that it is
zero.  We do a divide by len later in the function so that's not ok.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/pci/ttpci/av7110_av.c

@@ -1045,6 +1045,9 @@ static int play_iframe(struct av7110 *av7110, char __user *buf, unsigned int len
 
 	dprintk(2, "av7110:%p, \n", av7110);
 
+	if (len == 0)
+		return 0;
+
 	if (!(av7110->playing & RP_VIDEO)) {
 		if (av7110_av_start_play(av7110, RP_VIDEO) < 0)
 			return -EBUSY;