[llvm] [PowerPC][NFC] clean up if-else block in PPCRegisterInfo.cpp (PR #140084)

[Lei Huang via llvm-commits]

================
@@ -1610,62 +1610,69 @@ PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // Get the instruction opcode.
   unsigned OpC = MI.getOpcode();
 
-  if ((OpC == PPC::DYNAREAOFFSET || OpC == PPC::DYNAREAOFFSET8)) {
+  switch (OpC) {
----------------
lei137 wrote:

No, default handling is after the switch.  Can add:
```
default: break;
```

https://github.com/llvm/llvm-project/pull/140084