apibuild: Fix self.waring method call

The parameters of self.warning is inconsistent with its definition, So
fix it.

Signed-off-by: luzhipeng <luzhipeng@cestc.cn>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

scripts/apibuild.py

@@ -328,7 +328,7 @@ class index:
             if type in type_map:
                 type_map[type][name] = d
             else:
-                self.warning("Unable to register type ", type)
+                self.warning("Unable to register type %s" % type)
 
         if name == debugsym and not quiet:
             print("New symbol: %s" % (d))