thermal: tsens: Remove registering for Critical trip zone

The handle_critical_trips() api in thermal_core gets
invoked during the system resume path on 4.4 kernel.
If a thermal driver has registered for the critical trip
zone the handle_critical_trips() reads the current temperature
and checks against the critical threshold. If the
temperature value is greater than the critical threshold
the device is shutdown.

Remove registering the critical trip zone since its not
used by thermal sys clients. The driver will continue
to use it internally to set thresholds and monitor
the state of the TSENS (temperature sensor) controller.

Change-Id: Ie2024498224f078de77dd006d77cdfa99bb90eee
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>