sit: use kfree_skb to replace dev_kfree_skb

In failure case, we should use kfree_skb not
dev_kfree_skb to free skbuff, dev_kfree_skb
is defined as consume_skb.

Trace takes advantage of this point.
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/sit.c

@@ -951,7 +951,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 		if (!new_skb) {
 			ip_rt_put(rt);
 			dev->stats.tx_dropped++;
-			dev_kfree_skb(skb);
+			kfree_skb(skb);
 			return NETDEV_TX_OK;
 		}
 		if (skb->sk)
@@ -977,7 +977,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 tx_error_icmp:
 	dst_link_failure(skb);
 tx_error:
-	dev_kfree_skb(skb);
+	kfree_skb(skb);
 out:
 	dev->stats.tx_errors++;
 	return NETDEV_TX_OK;
@@ -1017,7 +1017,7 @@ static netdev_tx_t sit_tunnel_xmit(struct sk_buff *skb,
 
 tx_err:
 	dev->stats.tx_errors++;
-	dev_kfree_skb(skb);
+	kfree_skb(skb);
 	return NETDEV_TX_OK;
 
 }