Disable thermal throttle/shutdown

- The temperature we read back does not seem to be accurate, and varies
a lot unit-to-unit, perhaps due to bad calibration. Since the data is
not trustworthy, disable throttling based on it for the moment.

Change-Id: If01bd71ec7e1140a3ab257c96c4156c005519c5b
(cherry picked from commit 6c43d69508a8761a2cbfc886b77a56886740be64)