pinctrl: sx150x: make struct sx150x_regmap_config static

The structure sx150x_regmap_config is local to the source and does not
need to be in global scope, so make it static.

Cleans up sparse warning:
symbol 'sx150x_regmap_config' was not declared. Should it be static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinctrl-sx150x.c

@@ -1087,7 +1087,7 @@ static bool sx150x_reg_volatile(struct device *dev, unsigned int reg)
 	return reg == pctl->data->reg_irq_src || reg == pctl->data->reg_data;
 }
 
-const struct regmap_config sx150x_regmap_config = {
+static const struct regmap_config sx150x_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 32,