pinctrl: ti-iodelay: Constify struct regmap_config

`dra7_iodelay_regmap_config` is not modified and can be declared as
const to move its data to a read-only section.

The pointer used to reference that struct has been made const
accordingly.

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

drivers/pinctrl/ti/pinctrl-ti-iodelay.c

···
 	u32 reg_start_offset;
 	u32 reg_nr_per_pin;
 
-	struct regmap_config *regmap_config;
+	const struct regmap_config *regmap_config;
 };
 
 /**
···
 	return 0;
 }
 
-static struct regmap_config dra7_iodelay_regmap_config = {
+static const struct regmap_config dra7_iodelay_regmap_config = {
 	.reg_bits = 32,
 	.reg_stride = 4,
 	.val_bits = 32,