net: eqos: add function to get phy node and address

Since new atheros PHY driver needs to access its PHY node through
phy device, we have to assign the phy node in ethernet controller
driver. Otherwise the PHY driver will fail to get some nodes
and properties.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>