mfd: stw481x: Staticize stw481x_regmap_config

stw481x_regmap_config is local to this file.
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NSachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/stw481x.c

@@ -167,7 +167,7 @@ static struct mfd_cell stw481x_cells[] = {
 	},
 };
 
-const struct regmap_config stw481x_regmap_config = {
+static const struct regmap_config stw481x_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 };