ACPICA: fix acpi_serialize hang regression

patch 014d433f in mainline.

http://bugzilla.kernel.org/show_bug.cgi?id=8171



Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>