sctp: fix the return value of getting the sctp partial delivery point

Get the sctp partial delivery point using SCTP_PARTIAL_DELIVERY_POINT
socket option should return 0 if success, not -ENOTSUPP.
Signed-off-by: NWei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: NVlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -5053,7 +5053,7 @@ static int sctp_getsockopt_partial_delivery_point(struct sock *sk, int len,
 	if (copy_to_user(optval, &val, len))
 		return -EFAULT;
 
-	return -ENOTSUPP;
+	return 0;
 }
 
 /*