power: qpnp-fg-gen3: Add support to configure base termination current

Add support to configure base termination current which is the
upper boundary at which fuel gauge will signal an end of charge
to the charger during discharging.

Change-Id: Ied2f89fc8e132161d55a9bfbcca6738fef164b20
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>