ACPICA: Fix fault if acpi_terminate is called twice

Fixes a problem with the mechanism that prevents problems if the
acpi_terminate interface is inadvertently called more than once
before the ACPICA code is re-initialized. ACPICA BZ 795.

http://acpica.org/bugzilla/show_bug.cgi?id=795



Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>