netpoll: accept NULL np argument in netpoll_send_skb()

netpoll_send_skb() callers seem to leak skb if
the np pointer is NULL. While this should not happen, we
can make the code more robust.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index dfb4282..61b0de5 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -445,12 +445,11 @@ static inline netdev_tx_t dsa_slave_netpoll_send_skb(struct net_device *dev,
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	struct dsa_slave_priv *p = netdev_priv(dev);
 
-	if (p->netpoll)
-		netpoll_send_skb(p->netpoll, skb);
+	return netpoll_send_skb(p->netpoll, skb);
 #else
 	BUG();
-#endif
 	return NETDEV_TX_OK;
+#endif
 }
 
 static void dsa_skb_tx_timestamp(struct dsa_slave_priv *p,