[llvm] [AMDGPU] Flip the default value of maybeAtomic. NFCI. (PR #75220)

[Matt Arsenault via llvm-commits]

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@@ -29,6 +29,7 @@ class SM_Pseudo <string opName, dag outs, dag ins, string asmOps, list<dag> patt
   let mayStore = 0;
   let mayLoad = 1;
   let hasSideEffects = 0;
+  let maybeAtomic = 0;
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arsenm wrote:

Probably should fix this in a separate change 

https://github.com/llvm/llvm-project/pull/75220