ACPICA: Debugger: Fix "terminate" command by cleaning up subsystem shutdown logic

ACPICA commit 7e823714911480be47e310fb1b3590d289b9fd99

Segmentation fault can be seen for executing the "terminate" command. This
is because acpi_ut_subsystem_shutdown() is errnously called multiple times.

This patch cleans up acpi_ut_subsystem_shutdown() logics to fix this
issue. Lv Zheng.

Link: https://github.com/acpica/acpica/commit/7e823714


Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>