[llvm] [LoongArch] Override LoongArchTargetLowering::getExtendForAtomicCmpSwapArg (PR #83656)

[WÁNG Xuěruì via llvm-commits]

https://github.com/xen0n approved this pull request.

Should be good. Is the LA64 v1.10 work already underway? If not I'll probably handle some of these.

https://github.com/llvm/llvm-project/pull/83656