[llvm] [AMDGPU] Add pre-commit tests for PR90710. NFC. (PR #90711)

[Jay Foad via llvm-commits]

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@@ -0,0 +1,23 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
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jayfoad wrote:

Maybe call it `waitcnt-sample-waw.mir` by analogy with the existing `waitcnt-vmem-waw.mir`?

https://github.com/llvm/llvm-project/pull/90711