[llvm] [ARM] TableGen-erate node descriptions (PR #168212)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `bolt-aarch64-ubuntu-dylib` running on `bolt-worker-aarch64` while building `llvm` at step 2 "checkout".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/216/builds/833

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 2 (checkout) failure: update (failure)
git version 2.43.0
remote: Internal Server Error
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': The requested URL returned error: 500
remote: Internal Server Error
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': The requested URL returned error: 500

```

</details>

https://github.com/llvm/llvm-project/pull/168212