uboot-imx

net: keystone_net: register MDIO bus

Currently MDIO framework is not used to configure Ethernet PHY.
As result some of already implemented functions are duplicated.
So register MDIO bus in order to use it. On that stage it's just
registered, it'll be used as we start to use PHY framework.

Use mdio bus read/write/reset functions in the driver.

Acked-by: Vitaly Andrianov <vitalya@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>