power: qpnp-bms: detect constant voltage charging more accurately

Raise the CV charging threshold now that vddmax adjustments have been
implemented. Before, the BMS driver had to keep a 20 millivolt margin
because there was no guarantee that the charger will hit the set
max voltage. Now that the charger driver guarantees hitting within 5
millivolts of the max voltage, increase the CV detection threshold in
order to detect CV charging more accurately.

This change will smooth out the charging curve when the charger
transitions from CC to CV charging.

Change-Id: I0e399d9964866cc4cf2e7965f0d7d7be9bfab2ff
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>