Revert rG42230efccf8fe1185be5fa6c23dce0a8183d6ec9 "[DAG] Fold (sra (or (shl x,...

Revert rG42230efccf8fe1185be5fa6c23dce0a8183d6ec9 "[DAG] Fold (sra (or (shl x, c1), (shl y, c2)), c1) -> (sext_inreg (or x, (shl y,c2-c1)) iff c2 >= c1"

@foad was right - this isn't actually going to help with D136042 as much as hoped, we need a better AMDGPU-specific solution as other targets are likely to make use of it