docs: zh_CN: add iio index.rst translation

This patch translates Documentation/iio/index.rst into Chinese.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Huacai Chen <chenhuacai@kernel.org>
Link: https://lore.kernel.org/r/20210121033302.558935-3-siyanteng@loongson.cnSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/iio/index.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+.. include:: ../disclaimer-zh_CN.rst
+
+:Original: :doc:`../../../iio/index`
+:Translator: Yanteng Si <siyanteng@loongson.cn>
+
+.. _cn_iio_index:
+
+
+========
+工业 I/O
+========
+
+.. toctree::
+   :maxdepth: 1
+
+   iio_configfs
+
+   ep93xx_adc