net/rds: correct socket tunable error in rds_tcp_tune()

Correct an error where setting /proc/sys/net/rds/tcp/rds_tcp_rcvbuf would
instead modify the socket's sk_sndbuf and would leave sk_rcvbuf untouched.

Fixes: c6a58ffe ("RDS: TCP: Add sysctl tunables for sndbuf/rcvbuf on rds-tcp socket")
Signed-off-by: William Kucharski <william.kucharski@oracle.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/tcp.c

@@ -500,7 +500,7 @@ void rds_tcp_tune(struct socket *sock)
 		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
 	}
 	if (rtn->rcvbuf_size > 0) {
-		sk->sk_sndbuf = rtn->rcvbuf_size;
+		sk->sk_rcvbuf = rtn->rcvbuf_size;
 		sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
 	}
 	release_sock(sk);