[llvm] [AArch64] Remove wrong processor feature (PR #151289)

[Jon Roelofs via llvm-commits]

jroelofs wrote:

> No opinion on the change itself but your PR description does need more detail. A link to the change that added it would be good too.

I agree with David here, even after the edits. The description in the commit message needs to say "why" we are making the change, as in: why is this feature wrong and not preferred? That's something that often cannot be inferred from the "what" of the rest of the patch.

https://github.com/llvm/llvm-project/pull/151289