qom: Fix error message in object_class_property_add()

The error message in object_class_property_add() was copied from
object_property_add() in commit 16bf7f522a2ff. Clarify that it is
about a class, not an object.

While here, have the format string in both functions to fit in a
single line for better grep-ability, despite the checkpatch warning.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <157287383591.234942.311840593519058490.stgit@bahia.tlslab.ibm.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

qom/object.c

@@ -1106,9 +1106,8 @@ object_property_add(Object *obj, const char *name, const char *type,
     }
 
     if (object_property_find(obj, name, NULL) != NULL) {
-        error_setg(errp, "attempt to add duplicate property '%s'"
-                   " to object (type '%s')", name,
-                   object_get_typename(obj));
+        error_setg(errp, "attempt to add duplicate property '%s' to object (type '%s')",
+                   name, object_get_typename(obj));
         return NULL;
     }
 
@@ -1139,9 +1138,8 @@ object_class_property_add(ObjectClass *klass,
     ObjectProperty *prop;
 
     if (object_class_property_find(klass, name, NULL) != NULL) {
-        error_setg(errp, "attempt to add duplicate property '%s'"
-                   " to object (type '%s')", name,
-                   object_class_get_name(klass));
+        error_setg(errp, "attempt to add duplicate property '%s' to class (type '%s')",
+                   name, object_class_get_name(klass));
         return NULL;
     }