power: qpnp-fg-gen4: Qualify capacity learning start

Add support to qualify capacity learning start by reading
filtered battery current. Once the filtered battery current
goes below the user specified threshold, that is used to qualify
to start the capacity learning start. This improves the capacity
learning algorithm if the user re-inserts the charger when the
battery is not in a relaxed state.

Change-Id: I457b05edde1c0a1e13cb8cc67dd6b18bc19eef83
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>