mfd: Constify of_device_id array

of_device_id is always used as const.

(See driver.of_match_table and open firmware functions)
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/hi6421-pmic-core.c

@@ -93,7 +93,7 @@ static int hi6421_pmic_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static struct of_device_id of_hi6421_pmic_match_tbl[] = {
+static const struct of_device_id of_hi6421_pmic_match_tbl[] = {
 	{ .compatible = "hisilicon,hi6421-pmic", },
 	{ },
 };

drivers/mfd/rk808.c

@@ -246,7 +246,7 @@ static int rk808_remove(struct i2c_client *client)
 	return 0;
 }
 
-static struct of_device_id rk808_of_match[] = {
+static const struct of_device_id rk808_of_match[] = {
 	{ .compatible = "rockchip,rk808" },
 	{ },
 };

drivers/mfd/twl4030-power.c

@@ -829,7 +829,7 @@ static struct twl4030_power_data osc_off_idle = {
 	.board_config		= osc_off_rconfig,
 };
 
-static struct of_device_id twl4030_power_of_match[] = {
+static const struct of_device_id twl4030_power_of_match[] = {
 	{
 		.compatible = "ti,twl4030-power",
 	},