[turbofan] Rename floating point register / slot methods.

src/machine-type.h

Index: src/machine-type.h
diff --git a/src/machine-type.h b/src/machine-type.h
index 1085657894a94ea5a8d351496fd721d7861094a6..08786100b05c2ceaf88001c48ce871fc26499da8 100644
--- a/src/machine-type.h
+++ b/src/machine-type.h
@@ -177,7 +177,8 @@ std::ostream& operator<<(std::ostream& os, MachineType type);
 
 inline bool IsFloatingPoint(MachineRepresentation rep) {
   return rep == MachineRepresentation::kFloat32 ||
-         rep == MachineRepresentation::kFloat64;
+         rep == MachineRepresentation::kFloat64 ||
+         rep == MachineRepresentation::kSimd128;
 }
 
 // Gets the log2 of the element size in bytes of the machine type.