mfd: mc13xxx: i2c/spi: 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>
diff --git a/drivers/mfd/mc13xxx-i2c.c b/drivers/mfd/mc13xxx-i2c.c
index ae3addb..68b8448 100644
--- a/drivers/mfd/mc13xxx-i2c.c
+++ b/drivers/mfd/mc13xxx-i2c.c
@@ -46,7 +46,7 @@
 };
 MODULE_DEVICE_TABLE(of, mc13xxx_dt_ids);
 
-static struct regmap_config mc13xxx_regmap_i2c_config = {
+static const struct regmap_config mc13xxx_regmap_i2c_config = {
 	.reg_bits = 8,
 	.val_bits = 24,