docs/zh_CN: add core-api printk-basics.rst translation

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

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://lore.kernel.org/r/1610df76720b69f3f81bff27403e70e86c0875c5.1621239725.git.siyanteng@loongson.cn


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