iio: imu: st_lsm6dsx: remove invalid gain value for LSM9DS1

Get rid of invalid sensitivity value for LSM9DS1 gyro sensor

Fixes: 52f4b1f1 ("iio: imu: st_lsm6dsx: add support for accel/gyro unit of lsm9ds1")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>