net: use unlikely for dql_avail case

This is an unlikely case, use unlikely() on it seems logical.
Signed-off-by: xiaolinkui <xiaolinkui@kylinos.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -3272,7 +3272,7 @@ static inline void netdev_tx_completed_queue(struct netdev_queue *dev_queue,
 	 */
 	smp_mb();
 
-	if (dql_avail(&dev_queue->dql) < 0)
+	if (unlikely(dql_avail(&dev_queue->dql) < 0))
 		return;
 
 	if (test_and_clear_bit(__QUEUE_STATE_STACK_XOFF, &dev_queue->state))