doc: zh_CN: add translatation for debugfs.txt

Translate Documentation/filesystems/debugfs.txt into Chinese.

Signed-off-by: Chucheng Luo <luochucheng@vivo.com>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Wang Wenhu <wenhu.wang@vivo.com>
[rebase for upstream conflict and minor change of subject]
Link: https://lore.kernel.org/linux-doc/20200408021528.14062-1-luochucheng@vivo.com/
Link: https://lore.kernel.org/r/20200509080535.7625-1-wenhu.wang@vivo.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>