qom: add default value

qmp_qom_list_properties can print default values if they are available
as qmp_device_list_properties does, because both of them use the
ObjectPropertyInfo structure with default_value field. This can be useful
when working with "not device" types (e.g. memory-backend).

Signed-off-by: Maksim Davydov <davydov-max@yandex-team.ru>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240318213550.155573-2-davydov-max@yandex-team.ru>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

qom/qom-qmp-cmds.c

@@ -212,6 +212,7 @@ ObjectPropertyInfoList *qmp_qom_list_properties(const char *typename,
         info->name = g_strdup(prop->name);
         info->type = g_strdup(prop->type);
         info->description = g_strdup(prop->description);
+        info->default_value = qobject_ref(prop->defval);
 
         QAPI_LIST_PREPEND(prop_list, info);
     }