power: qpnp-fg-gen3: update default empty voltage to 2.85 V

Based on the hardware recommendation, update the default empty
voltage from 2.8 V to 2.85 V. This is to prevent undervolting
in low temperatures (e.g. -20 C) when battery voltage drops below
2.8 V but the battery SOC may not reach 0% as the charger is
configured to issue GP_FAULT2 when battery voltage goes below
2.8 V. This helps in shutting down graciously.

Change-Id: Ifc68b825541c09d985d890ee7200ff8e0af2ba0f
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>