docs: zh_CN: create the architecture-specific top-level directory

This mirrors commit 4f1bb0386d ("docs: create a top-level arch/
directory"), creating a top-level directory to hold architecture-specific
documentation.

Acked-by: Alex Shi <alexs@kernel.org>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/translations/zh_CN/arch/index.rst

@@ -8,12 +8,12 @@
 .. toctree::
    :maxdepth: 2
 
-   mips/index
-   arm64/index
-   riscv/index
-   openrisc/index
-   parisc/index
-   loongarch/index
+   ../mips/index
+   ../arm64/index
+   ../riscv/index
+   ../openrisc/index
+   ../parisc/index
+   ../loongarch/index
 
 TODOList:
 

Documentation/translations/zh_CN/index.rst

@@ -120,7 +120,7 @@ TODOList:
 .. toctree::
    :maxdepth: 2
 
-   arch
+   arch/index
 
 其他文档
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