net: mdio-gpio: Use devm_gpio_request_one instead of devm_gpio_request

Using devm_gpio_request_one lets us request gpio pins with initial state
in one go.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>