[llvm] [ARM] Fix failure to register-allocate CMP_SWAP_64 pseudo-inst (PR #104039)

[Matthias Braun via llvm-commits]

MatzeB wrote:

Seems though we are already doing similar sorting steps for the defs (which I think didn't exist when I initially wrote the pass) maybe it's just the price to pay to support more ISAs/features even if it makes the fast-regalloc slower... I guess pragmatically you can always check the compile-time-tracker to see how big of a compile-time effect this is...

https://github.com/llvm/llvm-project/pull/104039