Thermal/int340x: Handle properly the case when _trt or _art acpi entry is missing

If either of the entries was missing, the driver tried to free memory
using uninitialized pointer. In addition, it was dereferencing null
pointer.

Signed-off-by: Ilkka Koskinen <ilkka.koskinen@linux.intel.com>
Acked-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>