iio: ABI: document temperature and humidity peak/trough raw attributes

iio: ABI: document temperature and humidity peak/trough raw attributes

The in_temp_peak_raw attribute is already in use, but its documentation
is still missing. The in_humidityrelative_raw must be documented for a
new iio user that supports this attribute. Add temp and humidityrelative
use cases.
When at it, remove an extra blank space in the description.

For users that support minimum values, a new in_<type>_trough_raw
attribute is required. Add this attribute and document the first uses of
it for temp and humidityrelative types.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20231211122840.9760-1-579lpy@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>