e1000e: alternate MAC address update

If word 0x37 in the EEPROM is 0xFFFF _or_ 0x0000, then there is no
alternate MAC address in the EEPROM.

Signed-off-by: Bruce Allan <[e-mail]>
Tested-by: Aaron Brown <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>

drivers/net/e1000e/lib.c

···
 		goto out;
 	}
 
-	if (nvm_alt_mac_addr_offset == 0xFFFF) {
+	if ((nvm_alt_mac_addr_offset == 0xFFFF) ||
+	    (nvm_alt_mac_addr_offset == 0x0000))
 		/* There is no Alternate MAC Address */
 		goto out;
-	}
 
 	if (hw->bus.func == E1000_FUNC_1)
 		nvm_alt_mac_addr_offset += E1000_ALT_MAC_ADDRESS_OFFSET_LAN1;