power: pm8921-bms: disable ocv updates for flat portion of the curve

An issue is observed when an OCV is updated while the device is
sleeping. When it wakes up the SOC calculations are run on the new OCV
which result in a drastically different SOC than previously reported.
The root cause of this issue is PON OCV likely was unsettled.

Provide a feature where OCV updates can be disabled between certain
SOC range.

Change-Id: I54a75a7e9d05ff2c8ccd484850f02a0190d6a3b7
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>