net: phy: fixed: remove usage of a faux device

A struct mii_bus doesn't need a parent, so we can simplify the code and
remove using a faux device. Only difference is the following in sysfs
under /sys/class/mdio_bus:

old: fixed-0 -> '../../devices/faux/Fixed MDIO bus/mdio_bus/fixed-0'
new: fixed-0 -> ../../devices/virtual/mdio_bus/fixed-0

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://patch.msgid.link/e9426bb9-f228-4b99-bc09-a80a958b5a93@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>