This fixes the red LED shining up (signalizing low battery) when the battery is in fact far from being low. This happens because bq25895 ADC can't read any voltage lower than VSYS_MIN, so the red light used to be triggered anytime the voltage dropped below 3.7 V.
Based on schematics and datasheets, every component connected directly to VSYS is supposed to operate at least down to 3.3V.
Fixes #25 (closed)