Documentation:Update Documentation/zh_CN/arm64/memory.txt

This is a update of Chinese documentation:Documentation/zh_CN/arm64/memory.txt

It is based on the modifications of Documentation/arm64/memory.txt in submission:
"08375198", "4edae01e", "a24637d5", "383c2799".

Signed-off-by: Fu Wei <wefu@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>