power: supply: sc27xx: Calibrate the resistance of coulomb counter

There are some deviations between the real resistance and the ideal
resistance of coulomb counter, which will affect the accuracy of
the coulomb counter, thus calibrate the real resistance of coulomb
counter to improve the accuracy.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>