staging/octeon: Fix PHY binding in octeon-ethernet driver.

Commit d6c25beb

 (mdio-octeon: use an unique MDIO bus name.) changed the
names used to refer to MDIO buses.  The ethernet driver must be
changed to match, so that the PHY drivers can be attached.

Signed-off-by: David Daney <david.daney@cavium.com>
Acked-by: Florian Fainelli <florian@openwrt.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>