We avoid printing forward declarations and prototypes for most
types by sorting things topologically. But if structs nest we
do need the forward declarations, there's no other way.
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://lore.kernel.org/r/20231213231432.2944749-9-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>