mfd: 88pm860x-core: Constify struct regmap_config

The regmap_config struct may be const because it is not modified by the
driver and regmap_init() accepts pointer to const.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/88pm860x-core.c

@@ -1111,7 +1111,7 @@ static int verify_addr(struct i2c_client *i2c)
 	return 0;
 }
 
-static struct regmap_config pm860x_regmap_config = {
+static const struct regmap_config pm860x_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 };