ARM: dts: msm: Add a test thermal zone for SM8150

Add a sample thermal zone, which mitigates the cooling devices like
modem and display backlight for SM8150. This is a sample thermal zone,
which will be disabled by default.

Change-Id: I866b4c0c0b981960f9579501597d81cf258cd55f
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>