net: ethernet: dm9000: Handle -EPROBE_DEFER in dm9000_parse_dt()

The call to of_get_mac_address() can return -EPROBE_DEFER, for instance
when the MAC address is read from a NVMEM driver that did not probe yet.

Cc: H. Nikolaus Schaller <hns@goldelico.com>
Cc: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/davicom/dm9000.c

@@ -1405,6 +1405,8 @@ static struct dm9000_plat_data *dm9000_parse_dt(struct device *dev)
 	mac_addr = of_get_mac_address(np);
 	if (!IS_ERR(mac_addr))
 		ether_addr_copy(pdata->dev_addr, mac_addr);
+	else if (PTR_ERR(mac_addr) == -EPROBE_DEFER)
+		return ERR_CAST(mac_addr);
 
 	return pdata;
 }