power: qpnp-fg-gen4: add support for calibration configuration

Based on the hardware recommendation, add support for configuring
calibration level based on POWER_SUPPLY_PROP_CALIBRATE property.
Since this requires PBS trigger, add support to obtain PBS handle
to do the configuration.

Change-Id: If3ceb9a7ec3b4474f0db917d7c824a268411e91d
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>