net: dsa: support of_get_mac_address new ERR_PTR error

There was NVMEM support added to of_get_mac_address, so it could now
return ERR_PTR encoded error values, so we need to adjust all current
users of of_get_mac_address to this new fact.

While at it, remove superfluous is_valid_ether_addr as the MAC address
returned from of_get_mac_address is always valid and checked by
is_valid_ether_addr anyway.

Fixes: d01f449c ("of_net: add NVMEM support to of_get_mac_address")
Signed-off-by: Petr Štetiar <ynezz@true.cz>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/slave.c

@@ -1418,7 +1418,7 @@ int dsa_slave_create(struct dsa_port *port)
 				NETIF_F_HW_VLAN_CTAG_FILTER;
 	slave_dev->hw_features |= NETIF_F_HW_TC;
 	slave_dev->ethtool_ops = &dsa_slave_ethtool_ops;
-	if (port->mac && is_valid_ether_addr(port->mac))
+	if (!IS_ERR_OR_NULL(port->mac))
 		ether_addr_copy(slave_dev->dev_addr, port->mac);
 	else
 		eth_hw_addr_inherit(slave_dev, master);