tools/net/ynl: Add type info to struct members in generated docs

Extend the ynl doc generator to include type information for struct
members, ignoring the pad type.

Signed-off-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240129223458.52046-13-donald.hunter@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>