docs/zh_CN: add core api kobject translation

This patch translates Documentation/core-api/kobject.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/20210517133748.3461357-1-siyanteng@loongson.cn


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