iio: imu: st_lsm6dsx: do not access active-low/open-drain regs if not supported

Move active low and open drain register definitions in hw_settings
register map since not all supported sensors (e.g lsm9ds1) rely on the
same definitions

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>