[NFC][AArch64] Minor refactor of AArch64InstPrinter::printMatrixTileList

[david-arm]

Summary

We can remove the MatrixZADRegisterTable table of tile registers and
just calculate the register index directly.

llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp

void AArch64InstPrinter::printGPRSeqPairsClassOperand(const MCInst *MI,
   unsigned Sube = (size == 32) ? AArch64::sube32 : AArch64::sube64;
   unsigned Subo = (size == 32) ? AArch64::subo32 : AArch64::subo64;
 
   unsigned Even = MRI.getSubReg(Reg,  Sube);
   unsigned Odd = MRI.getSubReg(Reg,  Subo);
   O << getRegisterName(Even) << ", " << getRegisterName(Odd);
 }
 
-static const unsigned MatrixZADRegisterTable[] = {
-  AArch64::ZAD0, AArch64::ZAD1, AArch64::ZAD2, AArch64::ZAD3,
-  AArch64::ZAD4, AArch64::ZAD5, AArch64::ZAD6, AArch64::ZAD7
-};
-
 void AArch64InstPrinter::printMatrixTileList(const MCInst *MI, unsigned OpNum,
                                              const MCSubtargetInfo &STI,
                                              raw_ostream &O) {
   unsigned MaxRegs = 8;
   unsigned RegMask = MI->getOperand(OpNum).getImm();
 
   unsigned NumRegs = 0;
   for (unsigned I = 0; I < MaxRegs; ++I)
     if ((RegMask & (1 << I)) != 0)
       ++NumRegs;
 
   O << "{";
   unsigned Printed = 0;
   for (unsigned I = 0; I < MaxRegs; ++I) {
     unsigned Reg = RegMask & (1 << I);
     if (Reg == 0)
       continue;
-    O << getRegisterName(MatrixZADRegisterTable[I]);
+    O << getRegisterName(AArch64::ZAD0 + I);
     if (Printed + 1 != NumRegs)
       O << ", ";
     ++Printed;
   }
   O << "}";
 }
 
 void AArch64InstPrinter::printVectorList(const MCInst *MI, unsigned OpNum,