doc/zh-CN: Update cpu-freq/cpu-drivers.rst to make it more readable

There are some syntax errors in this document.
Also make it more readable.

Signed-off-by: Tang Yizhou <tangyizhou@huawei.com>
Acked-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/20211202050816.12240-1-tangyizhou@huawei.com


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