[llvm] [AArch64] Use nullptr instead of NULL (NFC) (PR #166083)

[Matt Arsenault via llvm-commits]

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@@ -37,9 +37,9 @@ static std::string AArch64InstPrinterTestPrintAlignedLabel(uint64_t value) {
   MCInstrInfo MII;
   MCRegisterInfo MRI;
   MCSubtargetInfo STI(Triple(""), "", "", "", {},
-                      ArrayRef((SubtargetFeatureKV *)NULL, (size_t)0),
-                      ArrayRef((SubtargetSubTypeKV *)NULL, (size_t)0), NULL,
-                      NULL, NULL, NULL, NULL, NULL);
+                      ArrayRef((SubtargetFeatureKV *)nullptr, (size_t)0),
+                      ArrayRef((SubtargetSubTypeKV *)nullptr, (size_t)0),
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arsenm wrote:

```suggestion
                      ArrayRef(),
                      ArrayRef(),
```

https://github.com/llvm/llvm-project/pull/166083