[llvm] [AMDGPU] Avoid repeated hash lookups (NFC) (PR #127573)

[Matt Arsenault via llvm-commits]

================
@@ -384,13 +384,14 @@ class AMDGPUWaitSGPRHazards {
       }
     }
 
-    bool Changed = State != BlockState[&MBB].Out;
+    auto &BS = BlockState[&MBB];
----------------
arsenm wrote:

No auto 

https://github.com/llvm/llvm-project/pull/127573