fou: avoid missing unlock in failure path

Fixes: 7a6c8c34 ("fou: implement FOU_CMD_GET")
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/fou.c

@@ -711,11 +711,10 @@ static int fou_nl_dump(struct sk_buff *skb, struct netlink_callback *cb)
 				    cb->nlh->nlmsg_seq, NLM_F_MULTI,
 				    skb, FOU_CMD_GET);
 		if (ret)
-			goto done;
+			break;
 	}
 	mutex_unlock(&fn->fou_lock);
 
-done:
 	cb->args[0] = idx;
 	return skb->len;
 }