[llvm] [Aarch64] Materialize immediates with 64-bit ORR + EOR if shorter (PR #68287)

[Dougall Johnson via llvm-commits]

dougallj wrote:

[Contributing to LLVM](https://llvm.org/docs/Contributing.html) asks me to select suitable reviewers – I don't think I have permission to do that on Github, but any chance of a review, @davemgreen or @resistor?

https://github.com/llvm/llvm-project/pull/68287