gpio: palmas: 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-palmas.c

@@ -148,7 +148,7 @@ static const struct palmas_device_data tps80036_dev_data = {
 	.ngpio = 16,
 };
 
-static struct of_device_id of_palmas_gpio_match[] = {
+static const struct of_device_id of_palmas_gpio_match[] = {
 	{ .compatible = "ti,palmas-gpio", .data = &palmas_dev_data,},
 	{ .compatible = "ti,tps65913-gpio", .data = &palmas_dev_data,},
 	{ .compatible = "ti,tps65914-gpio", .data = &palmas_dev_data,},