thermal: adc-tm: Add ADC_TM driver

ADC_TM driver is used by clients to set temperature thresholds
on channels supported by VADC peripheral. Clients can receive
notification once set thresholds are crossed. ADC_TM driver is
used by thermal driver and registers with of_thermal to let
thermal core set trip thresholds and read temperature for thermistors.

Change-Id: I49f57e3c6108b7976ad36a51f2c2f7a8e9eb5f2e
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>