thermal: qpnp-adc-tm: Support refreshed BTM driver

The BTM (Battery temperature module) peripheral driver
on the PMIC (Power management IC) supports threshold
monitoring and notifies clients when thresholds are crossed.
PMCOBALT supports refreshed BTM peripheral register interface
and the driver uses compatible property qpnp-adc-tm-hc to
distinguish using the refreshed peripheral. The external
client interface with the driver remains the same. Updates
include handling the interrupt when the thresholds are
crossed,programming the threholds and configuring
the hardware based on the refreshed design.

BTM peripheral needs the VADC_HC peripheral to compute the
gain/offset that are used to reverse compute the threhold
values to ADC code. Some of the reverse computation API's
such as calculating thermistor thresholds require the
gain and offset values before computing the ADC code to
be programmed. This requires modification to the existing
calibration API in the VADC_HC driver to calculate
the reference calibration points and store these values
for clients to use in the reverse computation

Change-Id: I989cfa4f40e7f1671f04dfa9d4c3fe2ccbbc44ab
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>