stmmac: fix oops on rmmod after assigning ip addr

An oops exists in the flow of stmmac_release().
phy_ethtool_get_wol() depends on phydev->drv.
phydev->drv will be null after stmmac_mdio_unreg() completes.

Steps to reproduce on Quark X1000:

1. ifconfig eth0 192.168.0.1
2. rmmod stmmac_pci

To fix this stmmac_mdio_unreg() should be run after unregister_netdev().
Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Reported-by: Dan O'Donovan <dan.odonovan@emutex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -2970,15 +2970,15 @@ int stmmac_dvr_remove(struct net_device *ndev)
 	priv->hw->dma->stop_tx(priv->ioaddr);
 
 	stmmac_set_mac(priv->ioaddr, false);
-	if (priv->pcs != STMMAC_PCS_RGMII && priv->pcs != STMMAC_PCS_TBI &&
-	    priv->pcs != STMMAC_PCS_RTBI)
-		stmmac_mdio_unregister(ndev);
 	netif_carrier_off(ndev);
 	unregister_netdev(ndev);
 	if (priv->stmmac_rst)
 		reset_control_assert(priv->stmmac_rst);
 	clk_disable_unprepare(priv->pclk);
 	clk_disable_unprepare(priv->stmmac_clk);
+	if (priv->pcs != STMMAC_PCS_RGMII && priv->pcs != STMMAC_PCS_TBI &&
+	    priv->pcs != STMMAC_PCS_RTBI)
+		stmmac_mdio_unregister(ndev);
 	free_netdev(ndev);
 
 	return 0;