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 have higher threshold by default.

Change-Id: I4564c742894713f7bd11c08e99e4c7ffb488904d
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>