power: step-chg: Fix VBAT based step chg flow

Currently, for VBAT based step charging, the uni-directional
forward flow of step charging algorithm works only in case of
tapered step charging mode. Extend the uni-directional flow
configuration to non-tapered step charging mode also.

Change-Id: I18267205abc643dddc735f071c5b368dbb0bca1a
Signed-off-by: Umang Agrawal <uagrawal@codeaurora.org>