[AArch64] Remove unused variable 'MaskSize' in GenerateFixedLengthSVETBL (NFC)

/llvm-project/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:26139:12: error: unused variable 'MaskSize' [-Werror,-Wunused-variable]
  unsigned MaskSize = ShuffleMask.size();
           ^
1 error generated.

Author: DamonFool

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -26136,7 +26136,6 @@ static SDValue GenerateFixedLengthSVETBL(SDValue Op, SDValue Op1, SDValue Op2,
   unsigned BitsPerElt = VTOp1.getVectorElementType().getSizeInBits();
   unsigned IndexLen = MinSVESize / BitsPerElt;
   unsigned ElementsPerVectorReg = VTOp1.getVectorNumElements();
-  unsigned MaskSize = ShuffleMask.size();
   uint64_t MaxOffset = APInt(BitsPerElt, -1, false).getZExtValue();
   assert(ElementsPerVectorReg <= IndexLen && ShuffleMask.size() <= IndexLen &&
          "Incorrectly legalised shuffle operation");