Add a kSimd128 machine type for Turbofan.

src/machine-type.cc

Index: src/machine-type.cc
diff --git a/src/machine-type.cc b/src/machine-type.cc
index 1fb886ca5254897f908c85e490318b62dc3e5705..fcc3e9797375bccd8b4c6b7a3c3e67a3d095d7db 100644
--- a/src/machine-type.cc
+++ b/src/machine-type.cc
@@ -26,6 +26,8 @@ std::ostream& operator<<(std::ostream& os, MachineRepresentation rep) {
       return os << "kRepFloat32";
     case MachineRepresentation::kFloat64:
       return os << "kRepFloat64";
+    case MachineRepresentation::kSimd128:
+      return os << "kRepSimd128";
     case MachineRepresentation::kTagged:
       return os << "kRepTagged";
   }