mlxsw: fix refcount leak in mlxsw_sp_port_lag_join()

In the Linux kernel, the following vulnerability has been resolved: mlxsw: fix refcount leak in mlxsw_sp_port_lag_join() When mlxsw_sp_port_lag_index_get() fails, mlxsw_sp_port_lag_join() returns an error without releasing the lag reference obtained by the earlier mlxsw_sp_lag_get(). All other error paths in the function jump to the cleanup label that ends with mlxsw_sp_lag_put(), so this is a single missed release. Fix the leak by replacing the bare 'return err' with a goto to the existing error cleanup label, which will drop the reference safely.