friend: Deduplicate interfaces

src/core/hle/service/friend/interface.h

@@ -0,0 +1,16 @@
+// Copyright 2018 yuzu emulator team
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "core/hle/service/friend/friend.h"
+
+namespace Service::Friend {
+
+class Friend final : public Module::Interface {
+public:
+    explicit Friend(std::shared_ptr<Module> module, const char* name);
+};
+
+} // namespace Service::Friend