[llvm] [AArch64][CodeGen] Add +lsfe atomicrmw tests where the result is unused. (PR #132022)

[Tomas Matheson via llvm-commits]

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

LGTM, thanks. This doesn't cover the equivalent LSE cases but at least we have LSFE covered.

https://github.com/llvm/llvm-project/pull/132022