thermal: core: Free tzp copy along with the thermal zone

The object pointed to by tz->tzp may still be accessed after being
freed in thermal_zone_device_unregister(), so move the freeing of it
to the point after the removal completion has been completed at which
it cannot be accessed any more.

Fixes: 3d439b1a ("thermal/core: Alloc-copy-free the thermal zone parameters structure")
Cc: 6.8+ <stable@vger.kernel.org> # 6.8+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://patch.msgid.link/4623516.LvFx2qVVIh@rjwysocki.net