net: phy: mdio: reset MDIO devices even if probe() is not implemented

Similarily to PHY drivers - there's no reason to require probe() to be
implemented in order to call mdio_device_reset(). MDIO devices can have
resets defined without needing to do anything in probe().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>