Split the three different uxBits checks in the PMIC task. 

This pull is more for comment & review rather than a firm pull request. I'm not sure whether submitting a pull request is appropriate or not.

The only significant difference occurs if the SAMPLE_RATE and CHAREG_STATE event flags are both set
simultaneously. Previously only the SAMPLE_RATE bit would be handled and cleared
for this case, now both will be processed. I don't know whether this makes a
difference in practice but it appears cleaner.

Is CHAREG_STATE a typo?