net: mdio-gpio: Add support for active low gpio pins

Some systems using mdio-gpio may use active-low gpio pins
(eg with inverters or FETs connected to all or some of the
gpio pins).

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc drivers/net/phy/mdio-gpio.c
Simple merge

diff --cc include/linux/mdio-gpio.h
Simple merge