object: return self in object_ref()

This allow for simpler assignment with ref: foo = object_ref(bar)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200110153039.1379601-19-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qom/object.h

@@ -1005,8 +1005,9 @@ GSList *object_class_get_list_sorted(const char *implements_type,
  *
  * Increase the reference count of a object.  A object cannot be freed as long
  * as its reference count is greater than zero.
+ * Returns: @obj
  */
-void object_ref(Object *obj);
+Object *object_ref(Object *obj);
 
 /**
  * object_unref:

qom/object.c

@@ -1107,12 +1107,13 @@ GSList *object_class_get_list_sorted(const char *implements_type,
                         object_class_cmp);
 }
 
-void object_ref(Object *obj)
+Object *object_ref(Object *obj)
 {
     if (!obj) {
-        return;
+        return NULL;
     }
     atomic_inc(&obj->ref);
+    return obj;
 }
 
 void object_unref(Object *obj)