power: qpnp-bms: compensate BMS OCVs

The BMS hardware takes an open circuit voltage at power-on. This
uses the VADC to do the conversion, so it must be compensated for.

Use the adc error compensation APIs to adjust the OCV reading.

Change-Id: I4722b4137ba31374d942cc2ea1d1936826c6228a
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>