[llvm] [AArch64] Add patterns for sub from add negative immediates (PR #156024)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm approved this pull request.

FYI: I have some WIP work to improve handling of INDEX, specifically to allow finer control for emitting a specific variant.

https://github.com/llvm/llvm-project/pull/156024