power: pm8921-bms: Fine tune SOC reporting during suspend/resume

Report SOC based on the time for which the system was suspended.

Remember -
1. If we recalculated the SOC in resume
2. The last_soc before going into suspend

Two cases arise - if we had a short suspend or if the suspend
was significant to case a drop in SOC. For the former do not
report a change in SOC and for the latter, report the
newly calculated_soc. In either of the cases, soc should not
increase because we cannot suspend while charging.

There is a possibility that the report_soc may be called
before BMS resume (update_power_supply), causing the driver
to report the old SOC. Handle this case by setting state
variables before recalculating the soc in resume.

CRs-Fixed: 482611
Change-Id: Ic21a24a1126800011f5e7e4531c1953436812811
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>