power: fg-alg: add min_start_soc to begin the capacity learning

Currently, capacity learning begins based on SOC threshold and
battery temperature. Since the SOC threshold to begin cannot be
qualified in certain low battery conditions, add another minimum
SOC threshold for a better qualification.

CRs-Fixed: 2225348
Change-Id: If916c0a04cec785dc25f3c70d0ea1643d598f479
Signed-off-by: Vamshi Krishna B V <vbv@codeaurora.org>