power: vm-bms: Manage the BMS states in software

Move the BMS design to s/w controlled FSM. This change
forces the BMS to operate in 2 states. The S2 state is forced
for all active scenarios (when the system is not suspended)
and while charging. The S3 state is forced if the system
goes to suspend.

This design simplifies the state management of BMS.

Change-Id: I4a0e92d9d5f4147b9bbf581aca9c8d83c66efd7a
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>