ACPICA: Dispatcher: Fix order issue of method termination

The last step of the method termination should be the end of the method
serialization. Otherwise, the steps happening after it will face the race
issues that cannot be protected by the method serialization mechanism.

This patch fixes this issue by moving the per-method-object deletion code
prior than the end of the method serialization. Otherwise, the possible
race issues may result in AE_ALREADY_EXISTS error in a parallel
environment.

Fixes: 74f51b80

 (ACPICA: Namespace: Fix dynamic table loading issues)
Reported-and-tested-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>