ACPICA: Fix to allow aliases within ASL namepaths

Fixes a problem where the use of an alias within a namepath
would result in a not found error or cause the compiler to fault.
Also now allows forward references from the Alias operator itself.
ACPICA BZ 738.

http://www.acpica.org/bugzilla/show_bug.cgi?id=738

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>

drivers/acpi/namespace/nsaccess.c

@@ -588,6 +588,10 @@ acpi_ns_lookup(union acpi_generic_state *scope_info,
 			 * segments).
 			 */
 			if (this_node->type == ACPI_TYPE_LOCAL_ALIAS) {
+				if (!this_node->object) {
+					return_ACPI_STATUS(AE_NOT_EXIST);
+				}
+
 				if (acpi_ns_opens_scope
 				    (((struct acpi_namespace_node *)this_node->
 				      object)->type)) {