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>

drivers/message/fusion/mptlan.c

@@ -703,7 +703,7 @@ mpt_lan_sdu_send (struct sk_buff *skb, struct net_device *dev)
 
 		printk (KERN_ERR "%s: no tx context available: %u\n",
 			__func__, priv->mpt_txfidx_tail);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	mf = mpt_get_msg_frame(LanCtx, mpt_dev);
@@ -713,7 +713,7 @@ mpt_lan_sdu_send (struct sk_buff *skb, struct net_device *dev)
 
 		printk (KERN_ERR "%s: Unable to alloc request frame\n",
 			__func__);
-		return 1;
+		return NETDEV_TX_BUSY;
 	}
 
 	ctx = priv->mpt_txfidx[priv->mpt_txfidx_tail--];