pinctrl: realtek: Constify struct regmap_config

`rtd_pinctrl_regmap_config` is not modified and can be declared as const
to move its data to a read-only section.

Signed-off-by: Javier Carrasco <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/realtek/pinctrl-rtd.c

···
 	.pin_config_group_set = rtd_pin_config_group_set,
 };
 
-static struct regmap_config rtd_pinctrl_regmap_config = {
+static const struct regmap_config rtd_pinctrl_regmap_config = {
 	.reg_bits = 32,
 	.val_bits = 32,
 	.reg_stride = 4,