net: fec_mxc: add unique bus and device names for DM_MDIO

net: fec_mxc: add unique bus and device names for DM_MDIO

When using DM_MDIO on SOC with more than one FEC and not sharing the MDIO
bus the name of the driver and the bus needs to be unique. Since name
used in device_bind_driver_to_node needs to be a static string, add the
string to the fec_priv struct and reuse fec_set_dev_name to generate the
name with the device sequence number.

Fixes: 3b8f99a3e762 ("net: fec: add support for DM_MDIO")
Signed-off-by: Markus Niebel <Markus.Niebel@ew.tq-group.com>
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Alexander Feilke <alexander.feilke@ew.tq-group.com>