mfd: tps65218: 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: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/tps65218.c

@@ -135,7 +135,7 @@ static const struct regmap_access_table tps65218_volatile_table = {
 	.n_yes_ranges = ARRAY_SIZE(tps65218_yes_ranges),
 };
 
-static struct regmap_config tps65218_regmap_config = {
+static const struct regmap_config tps65218_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.cache_type = REGCACHE_RBTREE,