docs/zh_CN: add core api cpu_hotplug translation

Translate Documentation/core-api/cpu_hotplug.rst into Chinese.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/5c2273563e64ccbbaf1e7ff043d2ab467879c421.1625798719.git.siyanteng@loongson.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/core-api/index.rst

@@ -80,12 +80,12 @@ Todolist:
    :maxdepth: 1
 
    cachetlb
+   cpu_hotplug
    genericirq
 
 Todolist:
 
 
-   cpu_hotplug
    memory-hotplug
    protection-keys