arm/dt: apq8084: Add VADC and ADC_TM node

VADC is used to measure ADC and clients include
reading the thermistors. ADC_TM is used for setting
recurring measurements on the ADC channel and notify
clients when set thresholds are crossed.

Change-Id: I1fedcee5e664d71ca23917b3912d30604e19277a
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>