net: mdio: setup of_node for the MDIO device

commit 00b73a5d71894521a0b4d1f1e53c91bede1aad5b from
git://source.codeaurora.org/external/qoriq/qoriq-components/linux



By mistake, the of_node of the MDIO device was not setup in the patch
linked below. As a consequence, any PHY driver that depends on the
of_node in its probe callback was not be able to successfully finish its
probe on a PHY, thus the Generic PHY driver was used instead.

Fix this by actually setting up the of_node.

Fixes: bc1bee3b ("net: mdiobus: Introduce fwnode_mdiobus_register_phy()")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
(cherry picked from commit a3afac4dbf76c448f211d914f379ba8dcabf393f)
Signed-off-by: Meng Li <Meng.Li@windriver.com>