rxrpc: Fix loss of final ack on shutdown

Fix the loss of transmission of a call's final ack when a socket gets shut
down.  This means that the server will retransmit the last data packet or
send a ping ack and then get an ICMP indicating the port got closed.  The
server will then view this as a failure.

Fixes: 3136ef49a1 ("rxrpc: Delay terminal ACK transmission on a client call")
Signed-off-by: David Howells <dhowells@redhat.com>

net/rxrpc/ar-internal.h

@@ -831,6 +831,7 @@ void rxrpc_clean_up_local_conns(struct rxrpc_local *);
  * conn_event.c
  */
 void rxrpc_process_connection(struct work_struct *);
+void rxrpc_process_delayed_final_acks(struct rxrpc_connection *, bool);
 
 /*
  * conn_object.c