mfd: pm8921-adc: Add BTM thermistor table

BTM (Battery Temperature Module) thermistor lookup
table is computed based on the resistor divider's
used on the board and the specifications of the
thermistor. Its a function of temperature vs the
ADC code for PM8921 ADC and is used to set the
cool/warm thresholds on the BTM.

CRs-Fixed: 299646
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>