net: designware: remove mdio bus on probe failure

net: designware: remove mdio bus on probe failure

The designware eth driver registers an mdio bus during probe, but if no
PHY is found, this bus is never removed although probe failes and the
driver is shown as not probed in the dm tree.

This later leads to errors when e.g. the mii or mdio commands try to
use available mdio buses because the mdio bus is still registered but
all corresponding data structures are invalid because probe failed.

Fix this by unregistering the mdio bus on probe failure (just as it is
unregistered in the .remove callback, too).

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>