hwmon: qpnp-adc-voltage: Add version check for VADC thermistor channels

pa-therm, xo_therm channels are used for reading the temperature.
Calibration type for above thermistor channels has to be absolute
for PM8950 1.0 and ratiometric for PM8950 2.0. Add version check to
detect the PMIC used and update the calibration type accordingly.

Change-Id: Iec4ed2ee5895feb91f74051a5ef060a19acb7ec0
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>