[clang] [test] Move CodeGen/aarch64-* into the AArch64 subfolder (PR #115818)

[Jonathan Thackray via cfe-commits]

https://github.com/jthackray commented:

You could also create an ARM/ directory, and move arm-* files into that too (186 files)

https://github.com/llvm/llvm-project/pull/115818