mptcp: Remove outdated and incorrect comment

mptcp_close() acquires the msk lock, so it clearly should not be held
before the function is called.
Signed-off-by: NMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/mptcp/protocol.c

@@ -1421,7 +1421,6 @@ static void mptcp_subflow_shutdown(struct sock *ssk, int how,
 	release_sock(ssk);
 }
 
-/* Called with msk lock held, releases such lock before returning */
 static void mptcp_close(struct sock *sk, long timeout)
 {
 	struct mptcp_subflow_context *subflow, *tmp;