power: vm-bms: Update OCV handling at end-of-charge

If the OCV drops after EOC (dropping the SOC) do not
apply any margin to maintain the SOC as 100. Allow
the SOC to change based on the OCV.

CRs-Fixed: 639617
Change-Id: I50ed0c893036749adea3c79cc44f958324efeba5
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>