The newly implemented fwnode_mdbiobus_register turned out to be
problematic - in case the fwnode_/of_/acpi_mdio are built as
modules, a dependency cycle can be observed during the depmod phase of
modules_install, eg.:

depmod: ERROR: Cycle detected: fwnode_mdio -> of_mdio -> fwnode_mdio
depmod: ERROR: Found 2 modules in dependency cycles!

OR:

depmod: ERROR: Cycle detected: acpi_mdio -> fwnode_mdio -> acpi_mdio
depmod: ERROR: Found 2 modules in dependency cycles!

A possible solution could be to rework fwnode_mdiobus_register,
so that to merge the contents of acpi_mdiobus_register and
of_mdiobus_register. However feasible, such change would
be very intrusive and affect huge amount of the of_mdiobus_register
users.

Since there are currently 2 users of ACPI and MDIO
(xgmac_mdio and mvmdio), withdraw the fwnode_mdbiobus_register
and roll back to a simple 'if' condition in affected drivers.

Fixes: 62a6ef6a ("net: mdiobus: Introduce fwnode_mdbiobus_register()")
Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Signed-off-by: David S. Miller <davem@davemloft.net>