Before this patch, we used to st ci->vcc_active depending on the
instantaneous ADC reading of VCC. Is it > .5v, we claim VCC is active,
and if it's below, VCC is inactive.
With this patch we move to an edge triggered approach: Only change
ci->vcc_active if the previous reading was different from the current
reading.
FIXME: why?
Change-Id: I71b703162219484e43638f1f2f692e9dd554ef55