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/drivers/net/tun.c b/drivers/net/tun.c
index b393536..c3927b4 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -398,12 +398,12 @@
 	if (tun->flags & TUN_FASYNC)
 		kill_fasync(&tun->fasync, SIGIO, POLL_IN);
 	wake_up_interruptible(&tun->socket.wait);
-	return 0;
+	return NETDEV_TX_OK;
 
 drop:
 	dev->stats.tx_dropped++;
 	kfree_skb(skb);
-	return 0;
+	return NETDEV_TX_OK;
 }
 
 static void tun_net_mclist(struct net_device *dev)