[compiler-rt] [compiler-rt][AArch64] Rewrite SME routines to all use __aarch64_cpu_features. (PR #119414)

[Jon Roelofs via llvm-commits]

jroelofs wrote:

> There's no immediate concern for Darwin because we have our own parallel implementations of the SME runtime routines.

Well, we have a downstream one. I think we should avoid making the upstream one incorrect and/or slower than it needs to be.

https://github.com/llvm/llvm-project/pull/119414