[AArch64] Simplify AES*Tied pseudo expansion (NFC).

[fhahn]

Summary

Suggested by @t.p.northover in https://bugs.llvm.org/show_bug.cgi?id=34015.

[t.p.northover]

LGTM.

lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp

case AArch64::CMP_SWAP_64:
     return expandCMP_SWAP(MBB, MBBI,
                           AArch64::LDAXRX, AArch64::STLXRX, AArch64::SUBSXrs,
                           AArch64_AM::getShifterImm(AArch64_AM::LSL, 0),
                           AArch64::XZR, NextMBBI);
   case AArch64::CMP_SWAP_128:
     return expandCMP_SWAP_128(MBB, MBBI, NextMBBI);
 
   case AArch64::AESMCrrTied:
-  case AArch64::AESIMCrrTied: {
-    MachineInstrBuilder MIB =
-    BuildMI(MBB, MBBI, MI.getDebugLoc(),
-            TII->get(Opcode == AArch64::AESMCrrTied ? AArch64::AESMCrr :
-                                                      AArch64::AESIMCrr))
-      .add(MI.getOperand(0))
-      .add(MI.getOperand(1));
-    transferImpOps(MI, MIB, MIB);
-    MI.eraseFromParent();
+  case AArch64::AESIMCrrTied:
+    MI.setDesc(TII->get(Opcode == AArch64::AESMCrrTied ? AArch64::AESMCrr :
+                                                         AArch64::AESIMCrr));
     return true;
-   }
-  }
   return false;
 }
 
 /// \brief Iterate over the instructions in basic block MBB and expand any
 /// pseudo instructions.  Return true if anything was modified.
 bool AArch64ExpandPseudo::expandMBB(MachineBasicBlock &MBB) {
   bool Modified = false;