[llvm] AArch64: Partially move setting of libcall names out of TargetLowering (PR #142985)

[Daniel Paoliello via llvm-commits]

https://github.com/dpaoliello requested changes to this pull request.

Please clean up the hexagon option (unless it is actually needed), otherwise the rest looks good.

https://github.com/llvm/llvm-project/pull/142985