gpio: mvebu: Make of_device_id array const

Make of_device_id array const, because all OF functions
handle it as const.
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mvebu.c

@@ -535,7 +535,7 @@ static void mvebu_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 #define mvebu_gpio_dbg_show NULL
 #endif
 
-static struct of_device_id mvebu_gpio_of_match[] = {
+static const struct of_device_id mvebu_gpio_of_match[] = {
 	{
 		.compatible = "marvell,orion-gpio",
 		.data       = (void *) MVEBU_GPIO_SOC_VARIANT_ORION,