docs/zh_CN: add virt guest-halt-polling translation

Translate Documentation/virt/guest-halt-polling.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/658e255eff55bfdadc1576107bf367a2e80b881a.1628212777.git.siyanteng@loongson.cn


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