Prevents a possible fault when a dynamic operation region is
deleted. ACPICA BZ 507.

http://acpica.org/bugzilla/show_bug.cgi?id=507Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>