[wasm] Support validation of asm.js modules with != 3 args.

src/ppc/macro-assembler-ppc.cc

Index: src/ppc/macro-assembler-ppc.cc
diff --git a/src/ppc/macro-assembler-ppc.cc b/src/ppc/macro-assembler-ppc.cc
index 9f808ff4c1f460ce6ab1ffcb98cecef8ed42aeca..9e936000f83ebd687f3e4b9afec13048ffb4891e 100644
--- a/src/ppc/macro-assembler-ppc.cc
+++ b/src/ppc/macro-assembler-ppc.cc
@@ -2767,7 +2767,9 @@ void MacroAssembler::CallRuntime(const Runtime::Function* f, int num_arguments,
   // arguments passed in because it is constant. At some point we
   // should remove this need and make the runtime routine entry code
   // smarter.
-  mov(r3, Operand(num_arguments));
+  if (num_arguments >= 0) {
+    mov(r3, Operand(num_arguments));
+  }
   mov(r4, Operand(ExternalReference(f, isolate())));
   CEntryStub stub(isolate(),
 #if V8_TARGET_ARCH_PPC64