drivers/net/ethernet/nxp/lpc_eth.c: Call mdiobus_unregister before mdiobus_free

Based on commit b27393ae

Calling mdiobus_free without calling mdiobus_unregister causes
BUG_ON(). This patch fixes the issue.

The semantic patch that found this issue(http://coccinelle.lip6.fr/):
// <smpl>
@@
expression E;
@@
  ... when != mdiobus_unregister(E);

+ mdiobus_unregister(E);
  mdiobus_free(E);
// </smpl>
Signed-off-by: NPeter Senna Tschudin <peter.senna@gmail.com>
Tested-by: NRoland Stigge <stigge@antcom.de>
Tested-by: NAlexandre Pereira da Silva <aletes.xgr@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/nxp/lpc_eth.c

@@ -1524,6 +1524,7 @@ static int lpc_eth_drv_remove(struct platform_device *pdev)
 				  pldat->dma_buff_base_p);
 	free_irq(ndev->irq, ndev);
 	iounmap(pldat->net_base);
+	mdiobus_unregister(pldat->mii_bus);
 	mdiobus_free(pldat->mii_bus);
 	clk_disable(pldat->clk);
 	clk_put(pldat->clk);