core: Move PageTable struct into Common.

src/core/memory_hook.cpp

@@ -1,11 +0,0 @@
-// Copyright 2018 Citra Emulator Project
-// Licensed under GPLv2 or any later version
-// Refer to the license.txt file included.
-
-#include "core/memory_hook.h"
-
-namespace Memory {
-
-MemoryHook::~MemoryHook() = default;
-
-} // namespace Memory