[turbofan] Fix machine signature allocation bug.

Review-Url: https://codereview.chromium.org/2670183004
Cr-Commit-Position: refs/heads/master@{#42921}

src/compiler/linkage.cc

@@ -52,8 +52,7 @@ std::ostream& operator<<(std::ostream& os, const CallDescriptor& d) {
 MachineSignature* CallDescriptor::GetMachineSignature(Zone* zone) const {
   size_t param_count = ParameterCount();
   size_t return_count = ReturnCount();
-  MachineType* types = reinterpret_cast<MachineType*>(
-      zone->New(sizeof(MachineType*) * (param_count + return_count)));
+  MachineType* types = zone->NewArray<MachineType>(param_count + return_count);
   int current = 0;
   for (size_t i = 0; i < return_count; ++i) {
     types[current++] = GetReturnType(i);