Fix the following checker warning:
	net/rxrpc/call_object.c:279 rxrpc_new_client_call()
	warn: passing zero to 'ERR_PTR'
where a value that's always zero is passed to ERR_PTR() so that it can be
passed to a tracepoint in an auxiliary pointer field.
Just pass NULL instead to the tracepoint.
Fixes: a84a46d73050 ("rxrpc: Add some additional call tracing")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
                goto error;
 
        trace_rxrpc_call(call, rxrpc_call_connected, atomic_read(&call->usage),
-                        here, ERR_PTR(ret));
+                        here, NULL);
 
        spin_lock_bh(&call->conn->params.peer->lock);
        hlist_add_head(&call->error_link,