NET: mdio-octeon: Enable the hardware before using it.

In some cases the mdio bus is not enabled at the time of probing.
This prevents anything from working, so we will enable it before
trying to use it, and disable it when the driver is removed.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
To: netdev@vger.kernel.org
To: gregkh@suse.de
Patchwork: http://patchwork.linux-mips.org/patch/1090/
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>