Remove now-superfluous HasCPACodegen() function

Author: rgwott

llvm/lib/Target/AArch64/AArch64Features.td

@@ -517,9 +517,6 @@ def FeaturePAuthLR : ExtensionWithMArch<"pauth-lr", "PAuthLR", "FEAT_PAuth_LR",
 def FeatureTLBIW : ExtensionWithMArch<"tlbiw", "TLBIW", "FEAT_TLBIW",
   "Enable Armv9.5-A TLBI VMALL for Dirty State">;
 
-def FeatureCPACodegen : SubtargetFeature<"cpa-codegen",
-  "HasCPACodegen", "true", "Generate scalar FEAT_CPA instructions">;
-
 //===----------------------------------------------------------------------===//
 //  Armv9.6 Architecture Extensions
 //===----------------------------------------------------------------------===//