ACPICA: Fix possible memory leak, error exit path

Fixed two possible memory leaks in the error exit paths of
acpi_ut_update_objerct_reference() and
acpi_ut_walk_package_tree()
These functions are similar in that they use a stack of state objects in
order to eliminate recursion. The stack must be fully deallocated
if an error occurs.

http://www.acpica.org/bugzilla/show_bug.cgi?id=383

Signed-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>