iio: dac: ltc2688: make ltc2688_dither_ext_info const

Add const qualifier to struct iio_chan_spec_ext_info
ltc2688_dither_ext_info[]. 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-16-v1-1-9b6514588b05@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: dlech

drivers/iio/dac/ltc2688.c

@@ -622,7 +622,7 @@ static const struct iio_chan_spec_ext_info ltc2688_toggle_ext_info[] = {
 	{ }
 };
 
-static struct iio_chan_spec_ext_info ltc2688_dither_ext_info[] = {
+static const struct iio_chan_spec_ext_info ltc2688_dither_ext_info[] = {
 	LTC2688_CHAN_EXT_INFO("dither_raw", LTC2688_INPUT_B, IIO_SEPARATE,
 			      ltc2688_dac_input_read, ltc2688_dac_input_write),
 	LTC2688_CHAN_EXT_INFO("dither_raw_available", LTC2688_INPUT_B_AVAIL,