docs/zh_CN: add pciebus-howto translation

Translate .../PCI/pciebus-howto.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/bd22bd2c4c1a9d869dbd69148a7b94b2e33f8e5c.1636683482.git.siyanteng@loongson.cn


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