Revert of Add U2F request state machines

device/u2f/u2f_return_code.h

Index: device/u2f/u2f_return_code.h
diff --git a/device/u2f/u2f_return_code.h b/device/u2f/u2f_return_code.h
deleted file mode 100644
index 4aa0b4284e73230357efcf7f347828c1ff4389f4..0000000000000000000000000000000000000000
--- a/device/u2f/u2f_return_code.h
+++ /dev/null
@@ -1,19 +0,0 @@
-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef DEVICE_U2F_U2F_RETURN_CODE_H_
-#define DEVICE_U2F_U2F_RETURN_CODE_H_
-
-namespace device {
-
-enum class U2fReturnCode : uint8_t {
-  SUCCESS,
-  FAILURE,
-  INVALID_PARAMS,
-  CONDITIONS_NOT_SATISFIED,
-};
-
-}  // namespace device
-
-#endif  // DEVICE_U2F_U2F_RETURN_CODE_H_