rxrpc: Fix ack.bufferSize to be 0 when generating an ack

ack.bufferSize should be set to 0 when generating an ack.

Fixes: 8d94aa38 ("rxrpc: Calls shouldn't hold socket refs")
Reported-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

net/rxrpc/output.c

@@ -97,7 +97,7 @@ static size_t rxrpc_fill_out_ack(struct rxrpc_connection *conn,
 	*_hard_ack = hard_ack;
 	*_top = top;
 
-	pkt->ack.bufferSpace	= htons(8);
+	pkt->ack.bufferSpace	= htons(0);
 	pkt->ack.maxSkew	= htons(0);
 	pkt->ack.firstPacket	= htonl(hard_ack + 1);
 	pkt->ack.previousPacket	= htonl(call->ackr_highest_seq);