power: smb-lib: Move to SW based step-charging

Remove the HW SOC-based step-charging logic and enable
SW based step-charging.

The SW based step-charging uses the periodic WD bark
IRQ to notify the battery properties. The bark-time
can be changes using the property 'qcom,wd-bark-time-secs'

'qcom,step-charging-enable' enables the feature.

Change-Id: Ib162f3eb3f98a4e7f144bedc8c8cea40fbf6137a
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>