thermal: tsens: Add tsens notify callback

TSENS driver does not handle the decision to shut down
the device on critical temperature events. The thermal
daemon is notified to take appropriate action.

The thermal sys framework expects the kernel driver to
handle critical events. If the kernel driver does not
have any provision to handle such events the thermal
sys takes action to shutdown the device. Adding the
notify api is to avoid such an action from the thermal sys.

Change-Id: I4bdddb5db040246df40389d3a487a22e66b0820f
Signed-off-by: Siddartha Mohanadoss <smohanad@codeaurora.org>