stmmac: priv->lock can be used uninitialized

To reproduce: if connman (http://connman.net/) is started,
inserting the stmmac module triggers a "BUG: spinlock bad magic on CPU#0".

Registering the device in stmmac_probe() sends a notification to connman
which brings the interface up before the lock is initialized.
Signed-off-by: NVlad Lungu <vlad.lungu@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/stmmac/stmmac_main.c

@@ -1509,6 +1509,8 @@ static int stmmac_probe(struct net_device *dev)
 		pr_warning("\tno valid MAC address;"
 			"please, use ifconfig or nwhwconfig!\n");
 
+	spin_lock_init(&priv->lock);
+
 	ret = register_netdev(dev);
 	if (ret) {
 		pr_err("%s: ERROR %i registering the device\n",
@@ -1520,8 +1522,6 @@ static int stmmac_probe(struct net_device *dev)
 	    dev->name, (dev->features & NETIF_F_SG) ? "on" : "off",
 	    (dev->features & NETIF_F_HW_CSUM) ? "on" : "off");
 
-	spin_lock_init(&priv->lock);
-
 	return ret;
 }