Staging: octeon-ethernet: Convert to use PHY Abstraction Layer.

The octeon-ethernet driver shares an mdio bus with the octeon-mgmt
driver.  Here we convert the octeon-ethernet driver to use the PHY
Abstraction Layer.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>