docs/zh_CN: update sysfs.txt about show() usage

Update the show() usage according to the English version.

Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Link: https://lore.kernel.org/r/20200610025333.84010-1-chenzhou10@huawei.com


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