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

Fixes: 622ec2c9 ("net: core: add UID to flows, rules, and routes")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>