docs/zh_CN: add core-api irq concepts.rst translation

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

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/22babdd7e3fa5121360eff875d005ba5f4647e21.1618568135.git.siyanteng@loongson.cn


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