power: qpnp-qg: Adjust the PON SOC based on cutoff & full-SOC

Adjust the PON SOC based on FULL and CUTOFF SOC to make sure
its scaled appropriately based on the float and cutoff-voltage
values.

Change-Id: I14b274dd7cad98b55fdce1aaa27783272231afd2
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>