mptcp: refer to 'MPTCP' socket in comments

We used to call it 'master' socket at the early stages of MPTCP
development, but the correct wording is 'MPTCP' socket opposed to 'TCP
subflows': convert the last 3 comments to use a more appropriate term.
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/mptcp/protocol.c

@@ -2202,7 +2202,7 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		if (skb_queue_empty(&msk->receive_queue) && __mptcp_move_skbs(msk))
 			continue;
 
-		/* only the master socket status is relevant here. The exit
+		/* only the MPTCP socket status is relevant here. The exit
 		 * conditions mirror closely tcp_recvmsg()
 		 */
 		if (copied >= target)
@@ -3521,7 +3521,7 @@ void mptcp_subflow_process_delegated(struct sock *ssk, long status)
 static int mptcp_hash(struct sock *sk)
 {
 	/* should never be called,
-	 * we hash the TCP subflows not the master socket
+	 * we hash the TCP subflows not the MPTCP socket
 	 */
 	WARN_ON_ONCE(1);
 	return 0;

net/mptcp/subflow.c

@@ -1719,7 +1719,7 @@ int mptcp_subflow_create_socket(struct sock *sk, unsigned short family,
 	mptcp_sockopt_sync_locked(mptcp_sk(sk), sf->sk);
 	release_sock(sf->sk);
 
-	/* the newly created socket really belongs to the owning MPTCP master
+	/* the newly created socket really belongs to the owning MPTCP
 	 * socket, even if for additional subflows the allocation is performed
 	 * by a kernel workqueue. Adjust inode references, so that the
 	 * procfs/diag interfaces really show this one belonging to the correct