[AArch64] Removing redundant PAuth flag

[tyb0807]

Summary

This removes HasPAUTH from AArch64SubTarget, as it seems to be a
redundant, unused copy of HasPAuth.

[MarkMurrayARM]

I see no problem with this.

[ab]

Same, makes sense, thanks!

llvm/lib/Target/AArch64/AArch64Subtarget.h

protected:
 
   // AppleA7 system register.
   bool HasAppleA7SysReg = false;
 
   // Future architecture extensions.
   bool HasETE = false;
   bool HasTRBE = false;
   bool HasBRBE = false;
-  bool HasPAUTH = false;
   bool HasSPE_EEF = false;
 
   // HasZeroCycleRegMove - Has zero-cycle register mov instructions.
   bool HasZeroCycleRegMove = false;
 
   // HasZeroCycleZeroing - Has zero-cycle zeroing instructions.
   bool HasZeroCycleZeroing = false;
   bool HasZeroCycleZeroingGP = false;
public:
   bool hasSSBS() const { return HasSSBS; }
   bool hasSB() const { return HasSB; }
   bool hasPredRes() const { return HasPredRes; }
   bool hasCCDP() const { return HasCCDP; }
   bool hasBTI() const { return HasBTI; }
   bool hasRandGen() const { return HasRandGen; }
   bool hasMTE() const { return HasMTE; }
   bool hasTME() const { return HasTME; }
-  bool hasPAUTH() const { return HasPAUTH; }
   // Arm SVE2 extensions
   bool hasSVE2AES() const { return HasSVE2AES; }
   bool hasSVE2SM4() const { return HasSVE2SM4; }
   bool hasSVE2SHA3() const { return HasSVE2SHA3; }
   bool hasSVE2BitPerm() const { return HasSVE2BitPerm; }
   bool hasMatMulInt8() const { return HasMatMulInt8; }
   bool hasMatMulFP32() const { return HasMatMulFP32; }
   bool hasMatMulFP64() const { return HasMatMulFP64; }