iio: imu: st_lsm6dsx: remove event_threshold field from hw struct

iio: imu: st_lsm6dsx: remove event_threshold field from hw struct

This field is used to store the wakeup event detection threshold value.
When adding support for more event types, some of which may have different
threshold values for different axes, storing all threshold values for all
event sources would be cumbersome. Thus, remove this field altogether, and
read the currently configured value from the sensor when requested by
userspace.

Signed-off-by: Francesco Lavra <flavra@baylibre.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>