iio: accel: bmi088: Constify struct regmap_bus

`bmi088_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-v1-3-34754f355b65@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/bmi088-accel-spi.c

@@ -36,7 +36,7 @@ static int bmi088_regmap_spi_read(void *context, const void *reg,
 	return spi_write_then_read(spi, addr, sizeof(addr), val, val_size);
 }
 
-static struct regmap_bus bmi088_regmap_bus = {
+static const struct regmap_bus bmi088_regmap_bus = {
 	.write = bmi088_regmap_spi_write,
 	.read = bmi088_regmap_spi_read,
 };