docs/zh_CN: fix devicetree usage-model translation

machine_desc is a item in devicetree, shouldn't be half translated. Let's
keep a whole word untranslated.

Signed-off-by: Huilong Deng <denghuilong@cdjrlc.com>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/20220510020135.55452-1-denghuilong@cdjrlc.com


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