message: Fix return value for device enumeration
  Summary: The function expects a Status
  Test Plan: All tests ok
  Reviewers: #tensorflow, hakons
diff: @@ -51,6 +51,7 @@ class XlaIpuDeviceFactory : public DeviceFactory {
  virtual Status ListPhysicalDevices(std::vector<string>* devices) override {
  devices->push_back(absl::StrCat("/physical_device:", DEVICE_XLA_IPU, ":0"));
  + return Status::OK();
  }
  };
  