iio: imu: st_lsm6dsx: add hw timestamp support

Introduce hw timestamp support instead of compute sample timestamps
according to interrupt rate and configured watermark. LSM6DSx based
devices are able to queue in hw FIFO the time reference of data
sampling

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
3 files changed