test/zns: fix kernel-doc-check warnings

Since the following warnings output.

$ ./scripts/kernel-doc-check test/zns.c
test/zns.c:3: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
test/zns.c:10: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Signed-off-by: Tokunori Ikegami <[email protected]>

Author: ikegami-t

libnvme/test/zns.c

@@ -1,12 +1,12 @@
 // SPDX-License-Identifier: LGPL-2.1-or-later
-/**
+/*
  * This file is part of libnvme.
  * Copyright (c) 2020 Western Digital Corporation or its affiliates.
  *
  * Authors: Keith Busch <[email protected]>
  */
 
-/**
+/*
  * Search out for ZNS type namespaces, and if found, report their properties.
  */
 #include "nvme/tree.h"