USB: cyberjack: fix buggy integer overflow test

"old_rdtodo" and "size" are short type.  They are type promoted to int
and the condition is never true.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/cyberjack.c

@@ -279,7 +279,7 @@ static void cyberjack_read_int_callback(struct urb *urb)
 
 		old_rdtodo = priv->rdtodo;
 
-		if (old_rdtodo + size < old_rdtodo) {
+		if (old_rdtodo > SHRT_MAX - size) {
 			dev_dbg(dev, "To many bulk_in urbs to do.\n");
 			spin_unlock(&priv->lock);
 			goto resubmit;