[turbofan] Exhaustive switches for MachineRepresentation.

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 423f6b307cf7926ea506c1e72d456df5ed90ca99..e6f0e1b1ea5f01e4b947021a25cfdf9b60c0cc1a 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -184,8 +184,6 @@ bool MachineTypeIsSubtype(MachineSemantic t1, MachineSemantic t2) {
       return t2 == MachineSemantic::kNumber || t2 == MachineSemantic::kAny;
     case MachineSemantic::kAny:
       return t2 == MachineSemantic::kAny;
-    default:
-      break;
   }
   UNREACHABLE();
   return false;
@@ -231,8 +229,6 @@ bool MachineRepresentationIsSubtype(MachineRepresentation r1,
              r2 == MachineRepresentation::kTagged;
     case MachineRepresentation::kTagged:
       return r2 == MachineRepresentation::kTagged;
-    default:
-      break;
   }
   UNREACHABLE();
   return false;