qapi/machine: Belatedly document target loongarch64 is since 7.1

Fixes: a8a506c39070 (hw/loongarch: Add support loongson3 virt machine type.)
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240718141001.3077709-1-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Song Gao <gaosong@loongson.cn>
1 file changed