Fix to return negative error code -ENOMEM from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 4a7f970f ("mlxsw: spectrum: Replace port_to_module array with array of structs")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>