power: qpnp-qg: Use both charge & discharge tables for PON SOC

To avoid a big SOC dump while moving between charge/discharge
profiles, use the average of charge and discharge SOC for PON
and GOOD OCV.

Change-Id: I02d88798cab2e2b5aeb13991586d9026c99dc922
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>