amt: fix error return code in amt_init()

Return error code when alloc_workqueue()
fails in amt_init().
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Taehee Yoo <ap420073@gmail.com>
Link: https://lore.kernel.org/r/20211102130353.1666999-1-yangyingliang@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/amt.c

@@ -3259,8 +3259,10 @@ static int __init amt_init(void)
 		goto unregister_notifier;
 
 	amt_wq = alloc_workqueue("amt", WQ_UNBOUND, 1);
-	if (!amt_wq)
+	if (!amt_wq) {
+		err = -ENOMEM;
 		goto rtnl_unregister;
+	}
 
 	spin_lock_init(&source_gc_lock);
 	spin_lock_bh(&source_gc_lock);