igb: Fix for Alt MAC Address feature on 82580 and later devices

In 82580 and later devices, the alternate MAC address feature is
completely handled by the option ROM and software does not handle
it anymore.  This patch changes the check_alt_mac_addr function to
exit immediately if device is 82580 or later.
Signed-off-by: Carolyn Wyborny <carolyn.wyborny@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/e1000_mac.c

@@ -191,6 +191,13 @@ s32 igb_check_alt_mac_addr(struct e1000_hw *hw)
 	u16 offset, nvm_alt_mac_addr_offset, nvm_data;
 	u8 alt_mac_addr[ETH_ALEN];
 
+	/*
+	 * Alternate MAC address is handled by the option ROM for 82580
+	 * and newer. SW support not required.
+	 */
+	if (hw->mac.type >= e1000_82580)
+		goto out;
+
 	ret_val = hw->nvm.ops.read(hw, NVM_ALT_MAC_ADDR_PTR, 1,
 				 &nvm_alt_mac_addr_offset);
 	if (ret_val) {