[llvm] [AMDGPU][NFC] Add test for 64-bit lshr with shifts >=32 (PR #138281)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,562 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+;; Test reduction of:
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arsenm wrote:

Can merge the test files 

https://github.com/llvm/llvm-project/pull/138281