ACPI: thermal: Fix a small leak in acpi_thermal_add()

Free "tz" if the "trip" allocation fails.

Fixes: 5fc2189f9335 ("ACPI: thermal: Create and populate trip points table earlier")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>