ACPICA: Fix extraneous warning if _DSM returns a package

_DSM can return any type of object, so validation on the return
type cannot be performed. ACPICA BZ 802.

http://www.acpica.org/bugzilla/show_bug.cgi?id=802



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>