thermal/debugfs: Free all thermal zone debug memory on zone removal

Because thermal_debug_tz_remove() does not free all memory allocated for
thermal zone diagnostics, some of that memory becomes unreachable after
freeing the thermal zone's struct thermal_debugfs object.

Address this by making thermal_debug_tz_remove() free all of the memory
in question.

Fixes: 7ef01f22 ("thermal/debugfs: Add thermal debugfs information for mitigation episodes")
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>