power: qcom: step-chg-jeita: Add support for OCV based step charging

Currently, step charging algorithm supports VBAT and SOC based
step charging. In addition, add OCV (Open Circuit Voltage) based
step charging which will be useful in certain hardware platforms
where OCV provides the proper threshold to switch between ranges.

Change-Id: I44d44759b18299d2aeb17d4ef4fd459eb07d6272
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>