net/fsl: xgmac_mdio: Fix incorrect iounmap when removing module

As reported by sparse: In the remove path, the driver would attempt to
unmap its own priv pointer - instead of the io memory that it mapped
in probe.

Fixes: 9f35a7342c ("net/fsl: introduce Freescale 10G MDIO driver")
Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/freescale/xgmac_mdio.c

@@ -331,9 +331,10 @@ err_ioremap:
 static int xgmac_mdio_remove(struct platform_device *pdev)
 {
 	struct mii_bus *bus = platform_get_drvdata(pdev);
+	struct mdio_fsl_priv *priv = bus->priv;
 
 	mdiobus_unregister(bus);
-	iounmap(bus->priv);
+	iounmap(priv->mdio_base);
 	mdiobus_free(bus);
 
 	return 0;