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/loopback.c b/drivers/net/loopback.c
index da472c6..51bbce7 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -89,7 +89,7 @@
 	} else
 		lb_stats->drops++;
 
-	return 0;
+	return NETDEV_TX_OK;
 }
 
 static struct net_device_stats *loopback_get_stats(struct net_device *dev)