mptcp: use _fast lock version in __mptcp_move_skbs

The function is short and won't sleep, so this can use the _fast version.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/protocol.c

@@ -1493,13 +1493,14 @@ static bool __mptcp_move_skbs(struct mptcp_sock *msk)
 	__mptcp_flush_join_list(msk);
 	do {
 		struct sock *ssk = mptcp_subflow_recv_lookup(msk);
+		bool slowpath;
 
 		if (!ssk)
 			break;
 
-		lock_sock(ssk);
+		slowpath = lock_sock_fast(ssk);
 		done = __mptcp_move_skbs_from_subflow(msk, ssk, &moved);
-		release_sock(ssk);
+		unlock_sock_fast(ssk, slowpath);
 	} while (!done);
 
 	if (mptcp_ofo_queue(msk) || moved > 0) {