docs/zh_CN: Improve zh_CN/process/howto.rst

   - Improve grammar of zh_CN/process/howto.rst.
   - Resolve potential problems in documentation.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/587fca686d8d7aa828dec2d803bf9f5d59819c57.1632389476.git.siyanteng@loongson.cn


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