dt-bindings: power: sc27xx: Add a new property to describe the real resistance of coulomb counter chip

Add a new property to describe the real resistance of coulomb counter chip,
which is used to calibrate the accuracy of the coulomb counter chip.
Acked-by: Rob Herring <robh@kernel.org>
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>