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/wan/wanxl.c b/drivers/net/wan/wanxl.c
index 8130b79..e4ad7b6 100644
--- a/drivers/net/wan/wanxl.c
+++ b/drivers/net/wan/wanxl.c
@@ -283,7 +283,7 @@
 #endif
 		netif_stop_queue(dev);
 		spin_unlock_irq(&port->lock);
-		return 1;       /* request packet to be queued */
+		return NETDEV_TX_BUSY;       /* request packet to be queued */
 	}
 
 #ifdef DEBUG_PKT