net: convert remaining non-symbolic return values in ndo_start_xmit() functions

This patch converts the remaining occurences of raw return values to their
symbolic counterparts in ndo_start_xmit() functions that were missed by the
previous automatic conversion.

Additionally code that assumed the symbolic value of NETDEV_TX_OK to be zero
is changed to explicitly use NETDEV_TX_OK.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/irda/sir_dev.c b/drivers/net/irda/sir_dev.c
index bde004f..71dce20 100644
--- a/drivers/net/irda/sir_dev.c
+++ b/drivers/net/irda/sir_dev.c
@@ -590,7 +590,7 @@
 	int err;
 	s32 speed;
 
-	IRDA_ASSERT(dev != NULL, return 0;);
+	IRDA_ASSERT(dev != NULL, return NETDEV_TX_OK;);
 
 	netif_stop_queue(ndev);