docs: deprecate kernel-doc-nano-HOWTO.txt

Now that the new Sphinx world order is taking over, the information in
kernel-doc-nano-HOWTO.txt is outmoded.  I hate to remove it altogether,
since it's one of those files that people expect to find.  But we can add a
warning and fix all the other pointers to it.

Reminded-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/Documentation/zh_CN/CodingStyle b/Documentation/zh_CN/CodingStyle
index bbb9d6a..1271779 100644
--- a/Documentation/zh_CN/CodingStyle
+++ b/Documentation/zh_CN/CodingStyle
@@ -399,7 +399,7 @@
 些事情的原因。
 
 当注释内核API函数时,请使用 kernel-doc 格式。请看
-Documentation/kernel-doc-nano-HOWTO.txt和scripts/kernel-doc 以获得详细信息。
+Documentation/kernel-documentation.rst和scripts/kernel-doc 以获得详细信息。
 
 Linux的注释风格是 C89 “/* ... */” 风格。不要使用 C99 风格 “// ...” 注释。