ACPICA: Add a lock to the internal object reference count mechanism

Certain external interfaces need to update object references
without holding the interpreter or namespace mutex objects. To
prevent race conditions, add a spinlock around the increment
and decrement of the reference counts for internal ACPI
objects. Reported by Andriy Gapon (avg@FreeBSD.org).

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