drivers/sensor: lps22hh: Enable fetching individual sensor channels

Add the possibility to fetch specific sensor channels independently,
either pressure data with SENSOR_CHAN_PRESS or temperature data
with SENSOR_CHAN_AMBIENT_TEMP.
Additionally, the option to fetch both channels simultaneously remains
available using SENSOR_CHAN_ALL, thus not breaking any samples.

Signed-off-by: Chris Braissant <chrisbraissant@gmail.com>