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/irda/au1k_ir.c b/drivers/net/irda/au1k_ir.c
index 269153e..c4361d4 100644
--- a/drivers/net/irda/au1k_ir.c
+++ b/drivers/net/irda/au1k_ir.c
@@ -512,13 +512,13 @@
 		printk(KERN_DEBUG "%s: tx_full\n", dev->name);
 		netif_stop_queue(dev);
 		aup->tx_full = 1;
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 	else if (((aup->tx_head + 1) & (NUM_IR_DESC - 1)) == aup->tx_tail) {
 		printk(KERN_DEBUG "%s: tx_full\n", dev->name);
 		netif_stop_queue(dev);
 		aup->tx_full = 1;
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	pDB = aup->tx_db_inuse[aup->tx_head];