s390x/cpumodel: Add missing visit_free

Beata Michalska noticed this missing visit_free() while reviewing
arm's implementation of qmp_query_cpu_model_expansion(), which is
modeled off this s390x implementation.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20191016145434.7007-1-drjones@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

target/s390x/cpu_models.c

@@ -515,6 +515,7 @@ static void cpu_model_from_info(S390CPUModel *model, const CpuModelInfo *info,
         visitor = qobject_input_visitor_new(info->props);
         visit_start_struct(visitor, NULL, NULL, 0, errp);
         if (*errp) {
+            visit_free(visitor);
             object_unref(obj);
             return;
         }