hwmon: qpnp-adc-voltage: Add temperature compensation for PM8909

Add VBAT and OCV temperature compensation for PM8909.
The temperature compensation is required on top of
gain/offset calibration to compensate for variations
due to chip revision, manufacturer and temperature.

Change-Id: Icc325a5e4e2ef0cbc1298a26da329510cd2c350b
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>