iio: imu: st_lsm6dsx: reset hw ts after resume

Reset hw time samples generator after system resume in order to avoid
disalignment between system and device time reference since FIFO
batching and time samples generator are disabled during suspend.

Fixes: 21345107 ("iio: imu: st_lsm6dsx: add hw timestamp support")
Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>