r8169: fix nic may not work after changing mac address.

When there is no AC power, NIC may not work after changing mac address.
Please refer to following link.
http://www.spinics.net/lists/netdev/msg356572.html

This issue is caused by runtime power management. When there is no AC
power, if we put NIC down (ifconfig down), the driver will be in runtime
suspend state and hardware will be put into D3 state. During this time,
driver cannot access hardware regisers. So if you set new mac address
during this time, it will not be set to hardware. After resume, NIC will
keep using the old mac address and the network will not work normally.

In this patch I add detecting runtime pm status when setting mac address.
If driver is in runtime suspend state, it will skip setting mac address, keep
the new mac address, and set the new mac address during runtime resume.

Signed-off-by: Chunhao Lin <hau@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169.c

@@ -4480,6 +4480,7 @@ static void rtl_rar_set(struct rtl8169_private *tp, u8 *addr)
 static int rtl_set_mac_address(struct net_device *dev, void *p)
 {
 	struct rtl8169_private *tp = netdev_priv(dev);
+	struct device *d = &tp->pci_dev->dev;
 	struct sockaddr *addr = p;
 
 	if (!is_valid_ether_addr(addr->sa_data))
@@ -4487,7 +4488,12 @@ static int rtl_set_mac_address(struct net_device *dev, void *p)
 
 	memcpy(dev->dev_addr, addr->sa_data, dev->addr_len);
 
-	rtl_rar_set(tp, dev->dev_addr);
+	pm_runtime_get_noresume(d);
+
+	if (pm_runtime_active(d))
+		rtl_rar_set(tp, dev->dev_addr);
+
+	pm_runtime_put_noidle(d);
 
 	return 0;
 }
@@ -7890,6 +7896,7 @@ static int rtl8169_runtime_resume(struct device *device)
 	struct pci_dev *pdev = to_pci_dev(device);
 	struct net_device *dev = pci_get_drvdata(pdev);
 	struct rtl8169_private *tp = netdev_priv(dev);
+	rtl_rar_set(tp, dev->dev_addr);
 
 	if (!tp->TxDescArray)
 		return 0;