[llvm] [DAGCombiner] Don't drop atomic property of original load. (PR #75626)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

We have various TLI.allowsMemoryAccess checks for load combines which should prevent merging consecutive atomic loads etc.

Is it worth doing the OriginalAlign fix as a preliminary patch? 

https://github.com/llvm/llvm-project/pull/75626