[llvm] fix a bug of PPCMIPeepholes which description in issue 71030 (PR #85451)

[Amy Kwan via llvm-commits]

================
@@ -525,6 +525,18 @@ def getAltVSXFMAOpcode : InstrMapping {
   let ValueCols = [["1"]];
 }
 
+def get64BitInstrFromSignedExt32BitInstr : InstrMapping {
+  let FilterClass = "SExt32To64";
+  // Instructions with the same opcode.
+  let RowFields = ["Inst"];
+  // Instructions with the same Interpretation64Bit value form a column.
+  let ColFields = ["Interpretation64Bit"];
+    // The key column are not the Interpretation64Bit-form instructions.
----------------
amy-kwan wrote:

```suggestion
   // The key column are not the Interpretation64Bit-form instructions.
```

https://github.com/llvm/llvm-project/pull/85451