clk: si570: 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>
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>

drivers/clk/clk-si570.c

@@ -393,7 +393,7 @@ static bool si570_regmap_is_writeable(struct device *dev, unsigned int reg)
 	}
 }
 
-static struct regmap_config si570_regmap_config = {
+static const struct regmap_config si570_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 	.cache_type = REGCACHE_RBTREE,