[Turbofan] Add Simd128 registers to RegisterConfiguration.

src/machine-type.h

Index: src/machine-type.h
diff --git a/src/machine-type.h b/src/machine-type.h
index 08786100b05c2ceaf88001c48ce871fc26499da8..efaf9e340dac2ae7881b9fbeecb6fb34b2abe648 100644
--- a/src/machine-type.h
+++ b/src/machine-type.h
@@ -23,8 +23,8 @@ enum class MachineRepresentation : uint8_t {
   kWord32,
   kWord64,
   kFloat32,
-  kFloat64,
-  kSimd128,
+  kFloat64,  // must follow kFloat32
+  kSimd128,  // must follow kFloat64
   kTagged
 };