power: qpnp-fg: configure fg termination current

The fuel gauge has a separate termination current from the charger.
This fuel gauge termination current controls when the fuel gauge will
report 100%, while the charger termination current controls when it will
stop charging.

Provide a device tree parameter in order to separately control this
property.

Change-Id: Ide262cd7f4af5c198ec2d55b45d107d6db12fbba
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>