selftests: make order checking verbose in msg_zerocopy selftest

We find that when lock debugging is on, notifications may not come in
order. Thus, we have order checking outputs managed by cfg_verbose, to
avoid too many outputs in this case.

Fixes: 07b65c5b ("test: add msg_zerocopy test")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@bytedance.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240701225349.3395580-3-zijianzhang@bytedance.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/msg_zerocopy.c

@@ -438,7 +438,7 @@ static bool do_recv_completion(int fd, int domain)
 	/* Detect notification gaps. These should not happen often, if at all.
 	 * Gaps can occur due to drops, reordering and retransmissions.
 	 */
-	if (lo != next_completion)
+	if (cfg_verbose && lo != next_completion)
 		fprintf(stderr, "gap: %u..%u does not append to %u\n",
 			lo, hi, next_completion);
 	next_completion = hi + 1;