mlxsw: Remove unused port_type_set devlink op

port_type_set devlink op is no longer used by any mlxsw driver,
so remove it.

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