netlink: specs: ovs: correct struct names

C codegen will soon support using struct types for binary attrs.
Correct the struct names in OvS specs.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20250506194101.696272-3-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>