iio: light: gp2ap002: Constify struct regmap_bus

`gp2ap002_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-v1-9-34754f355b65@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/gp2ap002.c

@@ -420,7 +420,7 @@ static int gp2ap002_regmap_i2c_write(void *context, unsigned int reg,
 	return i2c_smbus_write_byte_data(i2c, reg, val);
 }
 
-static struct regmap_bus gp2ap002_regmap_bus = {
+static const struct regmap_bus gp2ap002_regmap_bus = {
 	.reg_read = gp2ap002_regmap_i2c_read,
 	.reg_write = gp2ap002_regmap_i2c_write,
 };