mfd: max77693: Make of_device_id array const

Array of struct of_device_id may be be const as expected by
of_match_table field.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/max77693.c b/drivers/mfd/max77693.c
index c5535f0..7e05428 100644
--- a/drivers/mfd/max77693.c
+++ b/drivers/mfd/max77693.c
@@ -243,7 +243,7 @@
 };
 
 #ifdef CONFIG_OF
-static struct of_device_id max77693_dt_match[] = {
+static const struct of_device_id max77693_dt_match[] = {
 	{ .compatible = "maxim,max77693" },
 	{},
 };