OS should check whether the cooling device exists before it is unregistered.
If it doesn't exists, it is unnecessary to remove the sysfs link
and call the function of thermal_cooling_device_unregister.

http://bugzilla.kernel.org/show_bug.cgi?id=9982Signed-off-by: NZhao Yakui <yakui.zhao@intel.com>
Tested-by    : Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: NLen Brown <len.brown@intel.com>