iio: accel: adxl367: Constify struct regmap_bus

`adxl367_spi_regmap_bus` is not modified and can be declared as const to
move its data to a read-only section.
Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20240703-iio-cont-regmap_bus-v1-1-34754f355b65@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/adxl367_spi.c

@@ -72,7 +72,7 @@ static int adxl367_write(void *context, const void *val_buf, size_t val_size)
 	return spi_sync(st->spi, &st->reg_write_msg);
 }
 
-static struct regmap_bus adxl367_spi_regmap_bus = {
+static const struct regmap_bus adxl367_spi_regmap_bus = {
 	.read = adxl367_read,
 	.write = adxl367_write,
 };