of_batterydata: add properties for thermistor coefficients in GEN4 FG

Add the following properties that are needed for thermistor
coefficients configuration in GEN4 FG.
- qcom,therm-coefficients
- qcom,therm-center-offset

Change-Id: Id06a19eb23103c2b6566e6c8a3d8026444b46931
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>