Document that PCIe Gen5/Gen6 speeds are only in QAPI
since 9.0 - the rest is since 4.0.
Cc: Lukas Stockner <lstockner@genesiscloud.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Fixes: c08da86dc4 ("pcie: Support PCIe Gen5/Gen6 link speeds")
Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
1bdef7a629