Documentation/zh_CN: update Chinese version CodingStyle

Chinese version CodingStyle is a little outdate, it should be updated.

This patch sync with the latest CodingStyle of all changes,
new chapters (chapter 19 and chapter 20) have been translated.

Signed-off-by: Andy Deng <theandy.deng@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>