drivers: gpio_sifive: Add gpio_driver_data to driver data

Add gpio_driver_data as the first element in the driver data as the gpio
core expects this.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

drivers/gpio/gpio_sifive.c

@@ -48,6 +48,8 @@ struct gpio_sifive_config {
 };
 
 struct gpio_sifive_data {
+	/* gpio_driver_data needs to be first */
+	struct gpio_driver_data common;
 	/* list of callbacks */
 	sys_slist_t cb;
 };