igb: allow setting MAC address on i211 using a device tree blob

The Intel i211 LOM PCIe Ethernet controllers' iNVM operates as an OTP
and has no external EEPROM interface [1]. The following allows the
driver to pickup the MAC address from a device tree blob when CONFIG_OF
has been enabled.

[1]
http://www.intel.com/content/www/us/en/embedded/products/networking/i211-ethernet-controller-datasheet.html

Signed-off-by: John Holland <jotihojr@gmail.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -50,6 +50,7 @@
 #include <linux/aer.h>
 #include <linux/prefetch.h>
 #include <linux/pm_runtime.h>
+#include <linux/etherdevice.h>
 #ifdef CONFIG_IGB_DCA
 #include <linux/dca.h>
 #endif
@@ -2442,9 +2443,11 @@ static int igb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		break;
 	}
 
-	/* copy the MAC address out of the NVM */
-	if (hw->mac.ops.read_mac_addr(hw))
-		dev_err(&pdev->dev, "NVM Read Error\n");
+	if (eth_platform_get_mac_address(&pdev->dev, hw->mac.addr)) {
+		/* copy the MAC address out of the NVM */
+		if (hw->mac.ops.read_mac_addr(hw))
+			dev_err(&pdev->dev, "NVM Read Error\n");
+	}
 
 	memcpy(netdev->dev_addr, hw->mac.addr, netdev->addr_len);