[llvm] [AMDGPU] Refactor unit test. NFC (PR #82976)

[Matt Arsenault via llvm-commits]

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@@ -92,9 +92,23 @@ static const std::pair<StringRef, StringRef>
   W32FS = {"+wavefrontsize32", "w32"},
   W64FS = {"+wavefrontsize64", "w64"};
 
-static void testGPRLimits(
-    const char *RegName, bool TestW32W64,
-    std::function<bool(std::stringstream &, unsigned, GCNSubtarget &)> test) {
+using TestFuncTy =
+    std::function<bool(std::stringstream &, unsigned, const GCNSubtarget &)>;
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arsenm wrote:

can probably be function_ref? 

https://github.com/llvm/llvm-project/pull/82976