PPC: [wasm-simd] Fix S128Not on PPC

As this is a unary operation src operands must be the same.

Change-Id: Id6e3b11fdb942596c05c38591379e6d9fd71f19e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2332865Reviewed-by: Junliang Yan <jyan@ca.ibm.com>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#69234}

src/compiler/backend/ppc/code-generator-ppc.cc

@@ -2958,8 +2958,8 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     }
     case kPPC_S128Not: {
       Simd128Register dst = i.OutputSimd128Register();
-      Simd128Register src = i.InputSimd128Register(1);
-      __ vnor(dst, i.InputSimd128Register(0), src);
+      Simd128Register src = i.InputSimd128Register(0);
+      __ vnor(dst, src, src);
       break;
     }
     case kPPC_S128Select: {