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/s390/net/claw.c b/drivers/s390/net/claw.c
index f370f8d..c63babe 100644
--- a/drivers/s390/net/claw.c
+++ b/drivers/s390/net/claw.c
@@ -350,6 +350,8 @@
 	CLAW_DBF_TEXT_(4, trace, "clawtx%d", rc);
 	if (rc)
 		rc = NETDEV_TX_BUSY;
+	else
+		rc = NETDEV_TX_OK;
         return rc;
 }   /*  end of claw_tx */