net: use NETDEV_TX_OK instead of 0 in ndo_start_xmit() functions

This patch is the result of an automatic spatch transformation to convert
all ndo_start_xmit() return values of 0 to NETDEV_TX_OK.

Some occurences are missed by the automatic conversion, those will be
handled in a seperate patch.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ipip.c

diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 93e2b78..98075b6 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -486,7 +486,7 @@
 			stats->tx_dropped++;
 			dev_kfree_skb(skb);
 			tunnel->recursion--;
-			return 0;
+			return NETDEV_TX_OK;
 		}
 		if (skb->sk)
 			skb_set_owner_w(new_skb, skb->sk);
@@ -524,7 +524,7 @@
 
 	IPTUNNEL_XMIT();
 	tunnel->recursion--;
-	return 0;
+	return NETDEV_TX_OK;
 
 tx_error_icmp:
 	dst_link_failure(skb);
@@ -532,7 +532,7 @@
 	stats->tx_errors++;
 	dev_kfree_skb(skb);
 	tunnel->recursion--;
-	return 0;
+	return NETDEV_TX_OK;
 }
 
 static void ipip_tunnel_bind_dev(struct net_device *dev)