Do not include ID of the parent to mii_bus if that ID is negative since
it produces a rather confusing string (e.g. "mdio.11-1", which is very
likely to be interpreted as "mdio.11<dash>1").
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>