thermal: adc_tm: Support multiple driver instance

Support multiple instance of the ADC_TM device. Clients
need to register with the current ADC using the device
consumer name used to associate with the corresponding
phandle of the ADC_TM. Clients receive the device instance
which is to be used everytime an ADC request is made.

This change involves changing the interface to issue
ADC TM request and the corresponding clients changes.

Change-Id: Id7ecacddec0d37bf58275d489d55b830e8aef6be
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>