sh_eth: update OF PHY registeration

If the sh_eth device is registered using OF, then the driver
should call of_mdiobus_register() to register the PHYs described
in the devicetree and then use of_phy_connect() to connect the
PHYs to the device.

This ensures that any PHYs registered in the device tree are
appropriately connected to the parent devices nodes so that
the PHY drivers can access their OF properties.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>