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/donauboe.c b/drivers/net/irda/donauboe.c
index 1484c76..e4e9056 100644
--- a/drivers/net/irda/donauboe.c
+++ b/drivers/net/irda/donauboe.c
@@ -981,7 +981,7 @@
 
   self = netdev_priv(dev);
 
-  IRDA_ASSERT (self != NULL, return 0; );
+  IRDA_ASSERT (self != NULL, return NETDEV_TX_OK; );
 
   IRDA_DEBUG (1, "%s.tx:%x(%x)%x\n", __func__
       ,skb->len,self->txpending,INB (OBOE_ENABLEH));