Based on commit 
b27393aecf66199f5ddad37c302d3e0cfadbe6c0
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: Peter Senna Tschudin <peter.senna@gmail.com>
Tested-by: Roland Stigge <stigge@antcom.de>
Tested-by: Alexandre Pereira da Silva <aletes.xgr@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
 
                                  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);