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>
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 51f410e..a1d6045 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1063,14 +1063,14 @@
 		goto tx_err;
 
 	t->recursion--;
-	return 0;
+	return NETDEV_TX_OK;
 
 tx_err:
 	stats->tx_errors++;
 	stats->tx_dropped++;
 	kfree_skb(skb);
 	t->recursion--;
-	return 0;
+	return NETDEV_TX_OK;
 }
 
 static void ip6_tnl_set_cap(struct ip6_tnl *t)