USB 3.0 PHY is attached to the MDIO bus and should be supported
(accessed) as a MDIO device. This wasn't known initially which resulted
in writing driver that was working with MDIO bus (using some magic
values) without knowing it.
This commit updates DT to properly describe MDIO & USB 3.0 PHY and
enables required kernel drivers.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
