mlxsw: Ignore ports that are connected to eXtended mezanine

Use the info stored in the bus_info struct about the eXtended mezanine
connected ports and don't expose them.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>