[llvm] [AArch64] Consider COPY between disjoint register classes as expensive (PR #167661)

[Florian Hahn via llvm-commits]

https://github.com/fhahn approved this pull request.

LGTM, thanks.

Would be good to also update the PR title/description ot use cross-register bank instead of disjoint register classes.

https://github.com/llvm/llvm-project/pull/167661