Fix: sparse warning in inet_csk_prepare_forced_close

In e337e24d (inet: Fix kmemleak in tcp_v4/6_syn_recv_sock and
dccp_v4/6_request_recv_sock) I introduced the function
inet_csk_prepare_forced_close, which does a call to bh_unlock_sock().
This produces a sparse-warning.

This patch adds the missing __releases.
Signed-off-by: NChristoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/inet_connection_sock.c

@@ -735,6 +735,7 @@ EXPORT_SYMBOL(inet_csk_destroy_sock);
  * tcp/dccp_create_openreq_child().
  */
 void inet_csk_prepare_forced_close(struct sock *sk)
+	__releases(&sk->sk_lock.slock)
 {
 	/* sk_clone_lock locked the socket and set refcnt to 2 */
 	bh_unlock_sock(sk);