iio: dac: ad5770r: make ad5770r_rng_tbl const

Add const qualifier to struct ad5770r_output_modes ad5770r_rng_tbl[].
This is read-only data so it can be made const.

Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250628-iio-const-data-15-v1-1-b86ae055004c@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/dac/ad5770r.c

@@ -155,7 +155,7 @@ struct ad5770r_output_modes {
 	int max;
 };
 
-static struct ad5770r_output_modes ad5770r_rng_tbl[] = {
+static const struct ad5770r_output_modes ad5770r_rng_tbl[] = {
 	{ 0, AD5770R_CH0_0_300, 0, 300 },
 	{ 0, AD5770R_CH0_NEG_60_0, -60, 0 },
 	{ 0, AD5770R_CH0_NEG_60_300, -60, 300 },