[llvm] [AMDGPU] Refactor isDPALU_DPP to only check if the instruction requires the feature (PR #224373)

[Joe Nash via llvm-commits]

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@@ -5151,6 +5151,7 @@ bool AMDGPUAsmParser::validateDPP(const MCInst &Inst,
     unsigned DppCtrl = Inst.getOperand(DppCtrlIdx).getImm();
 
     if (!AMDGPU::isLegalDPALU_DPPControl(getSTI(), DppCtrl) &&
+        getSTI().hasFeature(AMDGPU::FeatureDPALU_DPP) &&
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Sisyph wrote:

Ok. I'm fine with keeping the functionality exactly the same in this patch. Please add NFC to the commit message.

https://github.com/llvm/llvm-project/pull/224373