power: pm8921-bms: change power on ocv if soc < 0

When a phone boots up with a weak battery the ocv (open circuit voltage)
is so low that we end up in  a -ve soc.

If a charger is plugged in, it takes a while for that -ve soc to reach
0. Until then the reported soc is returned 0. (note the driver
never reports a -ve soc). This creates an impression that it takes very
long to go from 0% to 1%.

Change this by bumping up the pon ocv a bit such that soc is reported
exact 0.

Change-Id: I3244723845920c9538dff7e72dab253fd4aa7e2b
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>