[X86] Remove getCPUKindCanonicalName which seems to be unused.

lib/Basic/Targets/X86.h

 #define PROC(ENUM, STRING, IS64BIT) CK_##ENUM,
 #include "clang/Basic/X86Target.def"
   } CPU = CK_Generic;
 
   bool checkCPUKind(CPUKind Kind) const;
 
   CPUKind getCPUKind(StringRef CPU) const;
 
-  std::string getCPUKindCanonicalName(CPUKind Kind) const;
-
   enum FPMathKind { FP_Default, FP_SSE, FP_387 } FPMath = FP_Default;
 
 public:
   X86TargetInfo(const llvm::Triple &Triple, const TargetOptions &)
       : TargetInfo(Triple) {
     LongDoubleFormat = &llvm::APFloat::x87DoubleExtended();
   }
 

lib/Basic/Targets/X86.cpp

void X86TargetInfo::getCPUSpecificCPUDispatchFeatures(
   StringRef WholeList =
       llvm::StringSwitch<StringRef>(CPUSpecificCPUDispatchNameDealias(Name))
 #define CPU_SPECIFIC(NAME, MANGLING, FEATURES) .Case(NAME, FEATURES)
 #include "clang/Basic/X86Target.def"
           .Default("");
   WholeList.split(Features, ',', /*MaxSplit=*/-1, /*KeepEmpty=*/false);
 }
 
-std::string X86TargetInfo::getCPUKindCanonicalName(CPUKind Kind) const {
-  switch (Kind) {
-  case CK_Generic:
-    return "";
-#define PROC(ENUM, STRING, IS64BIT)                                            \
-  case CK_##ENUM:                                                              \
-    return STRING;
-#include "clang/Basic/X86Target.def"
-  }
-  llvm_unreachable("Invalid CPUKind");
-}
-
 // We can't use a generic validation scheme for the cpus accepted here
 // versus subtarget cpus accepted in the target attribute because the
 // variables intitialized by the runtime only support the below currently
 // rather than the full range of cpus.
 bool X86TargetInfo::validateCpuIs(StringRef FeatureStr) const {
   return llvm::StringSwitch<bool>(FeatureStr)
 #define X86_VENDOR(ENUM, STRING) .Case(STRING, true)
 #define X86_CPU_TYPE_COMPAT_WITH_ALIAS(ARCHNAME, ENUM, STR, ALIAS)             \