netlink: specs: correct types of legacy arrays

ethtool has some attrs which dump multiple scalars into
an attribute. The spec currently expects one attr per entry.

Fixes: a353318e

 ("tools: ynl: populate most of the ethtool spec")
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230526220653.65538-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>