Similar to the way in which of_mdiobus_register() has a fallback to the
non-DT based mdiobus_register() when CONFIG_OF is not set, we can create
a shim for the device-managed devm_of_mdiobus_register() which calls
devm_mdiobus_register() and discards the struct device_node *.

In particular, this solves a build issue with the qca8k DSA driver which
uses devm_of_mdiobus_register and can be compiled without CONFIG_OF.
Reported-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NVladimir Oltean <olteanv@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>