power: Only go into ALS callback if HasAmbientLight changed
Ambient light sensors can be quite sensitive and the LightLevel property might be changing very often. That has two undesired consequences:
- The
als_enabled_state_changed
callback gets constantly called due to a change in a property which it does not care about, as onlyHasAmbientLight
is relevant. - During debugging, the terminal gets spammed with "ALS enabled: on/off" messages.