net: fou: regenerate the uAPI from the spec

Regenerate the FOU uAPI header from the YAML spec.

The flags now come before attributes which use them,
and the comments for type disappear (coders should look
at the spec instead).

Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>