power: pm8921-bms: adjust rbatt and ocv both for shutdown soc

When ocv (open circuit voltage of the battery) is adjusted to match a
specific soc, rbatt (the battery resistance) changes too. This is because
rbatt is dependent on the remaining charge which changes as the ocv
changes.

The issue we observed with this changing rbatt was the unusable charge
changes which causes the soc to move away from the soc the algorithm
attempts to match.

To get around this issue adjust both the rbatt and ocv when we want to
match a soc for a specific soc.

Change-Id: Ifa8efe1e37b9982d6d67730f911e47e369e9b4ff
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>