net: dsa: mt7530: Include gpio/consumer.h for GPIO functions

Fixes build errors seen with CONFIG_GPIOLIB disabled and warnings enabled:

drivers/net/dsa/mt7530.c: In function 'mt7530_setup':
drivers/net/dsa/mt7530.c:948:3: error: implicit declaration of function 'gpiod_set_value_cansleep' [-Werror=implicit-function-declaration]
   gpiod_set_value_cansleep(priv->reset, 0);
   ^~~~~~~~~~~~~~~~~~~~~~~~
drivers/net/dsa/mt7530.c: In function 'mt7530_probe':
drivers/net/dsa/mt7530.c:1068:17: error: implicit declaration of function 'devm_gpiod_get_optional' [-Werror=implicit-function-declaration]
   priv->reset = devm_gpiod_get_optional(&mdiodev->dev, "reset",
                 ^~~~~~~~~~~~~~~~~~~~~~~
drivers/net/dsa/mt7530.c:1069:13: error: 'GPIOD_OUT_LOW' undeclared (first use in this function)
             GPIOD_OUT_LOW);
             ^~~~~~~~~~~~~
drivers/net/dsa/mt7530.c:1069:13:

Fixes: b8f126a8 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>