qmp: improve error reporting for -object and object-add

Use QERR_INVALID_PARAMETER_VALUE for consistency.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

qmp.c

@@ -540,7 +540,7 @@ void object_add(const char *type, const char *id, const QDict *qdict,
 
     klass = object_class_by_name(type);
     if (!klass) {
-        error_setg(errp, "invalid class name");
+        error_setg(errp, "invalid object type: %s", type);
         return;
     }