arm/dt: Add new VADC nodes

Add new VADC nodes to read PA THERM's, MSM THERM's
and EMMC THERM. The VADC nodes for the thermistors
uses the 100k pull-up option. If clients need a 150k
pull-up option they need to add/edit the appropriate
channel id's and scaling functions to use the 150k
pull-up configuration.

Change-Id: Ifbd77b8da7e32be0b994624305dfac60883b284e
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>