net: use symbolic values for ndo_start_xmit() return codes

Convert magic values 1 and -1 to NETDEV_TX_BUSY and NETDEV_TX_LOCKED respectively.

0 (NETDEV_TX_OK) is not changed to keep the noise down, except in very few cases
where its in direct proximity to one of the other values.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/au1000_eth.c b/drivers/net/au1000_eth.c
index d58c105..d3c734f 100644
--- a/drivers/net/au1000_eth.c
+++ b/drivers/net/au1000_eth.c
@@ -957,7 +957,7 @@
 		/* We've wrapped around and the transmitter is still busy */
 		netif_stop_queue(dev);
 		aup->tx_full = 1;
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 	else if (buff_stat & TX_T_DONE) {
 		update_tx_stats(dev, ptxd->status);