Fix to return error code -EINVAL instead of 0 if optlen is invalid.

Fixes: 01d2f7e2 ("net/smc: sockopts TCP_NODELAY and TCP_CORK")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>