net: macb: support of_get_mac_address new ERR_PTR error

There was NVMEM support added directly to of_get_mac_address, and it uses
nvmem_get_mac_address under the hood, so we can remove it. As
of_get_mac_address can now return ERR_PTR encoded error values, adjust to
that as well.
Signed-off-by: NPetr Štetiar <ynezz@true.cz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -4137,15 +4137,13 @@ static int macb_probe(struct platform_device *pdev)
 		bp->rx_intr_mask |= MACB_BIT(RXUBR);
 
 	mac = of_get_mac_address(np);
-	if (mac) {
+	if (PTR_ERR(mac) == -EPROBE_DEFER) {
+		err = -EPROBE_DEFER;
+		goto err_out_free_netdev;
+	} else if (!IS_ERR(mac)) {
 		ether_addr_copy(bp->dev->dev_addr, mac);
 	} else {
-		err = nvmem_get_mac_address(&pdev->dev, bp->dev->dev_addr);
-		if (err) {
-			if (err == -EPROBE_DEFER)
-				goto err_out_free_netdev;
-			macb_get_hwaddr(bp);
-		}
+		macb_get_hwaddr(bp);
 	}
 
 	err = of_get_phy_mode(np);