ARM: dts: msm: Add pa_therm vadc channel to thermal zone for msm8909

Add pa_therm0 vadc channel to thermal zone to provide thermal clients
the ability to read pa_therm0 under thermal framework for msm8909.

Change-Id: I04e1d4649ce1ae411267306244730d7e24db5154
Signed-off-by: Rama Krishna Phani A <rphani@codeaurora.org>