[ddk][usb] Delete <ddk/protocol/usb.h> header
This will soon be replaced by a banjo library.
In the mean time, use <ddk/protocol/usb-old.h> instead.
TEST: garnet builds
Change-Id: Ibfd6ac579d15fca4c10c5c45fdf791a5447be001
diff --git a/system/ulib/ddk/include/ddk/protocol/usb.h b/system/ulib/ddk/include/ddk/protocol/usb.h
deleted file mode 100644
index 2a9a00f..0000000
--- a/system/ulib/ddk/include/ddk/protocol/usb.h
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2018 The Fuchsia Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#pragma once
-
-#include <ddk/protocol/usb-old.h>
