power: pm8921-bms: Add connector resistance

The current software does not take in to account the resistance
introduced because of the battery connectors and rsense. This
needs to be accounted for when the battery resistance is
calculated.

Change-Id: I0f2b440bae8168868b26f35c8ec59a21d4906f0f
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>