[llvm] [AArch64] Improve code generation for experimental.cttz.elts (PR #91505)

[David Sherwood via llvm-commits]

david-arm wrote:

> Do the cost estimates @david-arm added recently also need updating after lowering improvements?

They will yes. It's on our TODO list. :)

https://github.com/llvm/llvm-project/pull/91505