Add mpu driver and remove interface library
from drivers

Add mpu driver for upstreaming

After removing of interface library,targets and applications
will list explicitly which libraries to link

Change-Id: Icfa449a2981093161f283e45b4d52ca6199371b8
diff --git a/drivers/mhu_dummy/include/mhu_dummy.hpp b/drivers/mhu_dummy/include/mhu_dummy.hpp
new file mode 100644
index 0000000..d04fe1c
--- /dev/null
+++ b/drivers/mhu_dummy/include/mhu_dummy.hpp
@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2020-2021 Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed under the Apache License, Version 2.0 (the License); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an AS IS BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef MHU_DUMMY_HPP
+#define MHU_DUMMY_HPP
+
+#include <mailbox.hpp>
+
+namespace Mailbox {
+
+class MHUDummy : public Mailbox {
+public:
+    MHUDummy();
+    virtual ~MHUDummy();
+    virtual bool sendMessage() final;
+    virtual void handleMessage() final;
+};
+
+} // namespace Mailbox
+
+#endif /* #ifndef MHU_DUMMY_HPP */