[llvm] [AArch64MIPeepholeOpt] Coalesce sibling base-address materializations (PR #223682)

[Nashe Mncube via llvm-commits]

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

Thanks for breaking the patches up. Some minor commits from my first passthrough

https://github.com/llvm/llvm-project/pull/223682