Kernel: Move the Storage directory to be a new directory under Devices

The Storage subsystem, like the Audio and HID subsystems, exposes Unix
device files (for example, in the /dev directory). To ensure consistency
across the repository, we should make the Storage subsystem to reside in
the Kernel/Devices directory like the two other mentioned subsystems.

Kernel/Devices/Storage/StorageController.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2020, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/OwnPtr.h>
+#include <Kernel/Bus/PCI/Access.h>
+#include <Kernel/Bus/PCI/Device.h>
+#include <Kernel/Devices/Device.h>
+#include <Kernel/Library/LockRefPtr.h>
+#include <Kernel/Locking/Mutex.h>
+#include <Kernel/Memory/PhysicalPage.h>
+#include <Kernel/PhysicalAddress.h>
+#include <Kernel/Random.h>
+#include <Kernel/WaitQueue.h>
+
+namespace Kernel {
+
+class AsyncBlockDeviceRequest;
+class StorageDevice;
+class StorageController : public AtomicRefCounted<StorageController> {
+
+public:
+    virtual ~StorageController() = default;
+
+    virtual LockRefPtr<StorageDevice> device(u32 index) const = 0;
+    virtual size_t devices_count() const = 0;
+
+    u32 controller_id() const { return m_controller_id; }
+    u32 hardware_relative_controller_id() const { return m_hardware_relative_controller_id; }
+
+protected:
+    virtual ErrorOr<void> reset() = 0;
+    virtual ErrorOr<void> shutdown() = 0;
+
+    virtual void complete_current_request(AsyncDeviceRequest::RequestResult) = 0;
+
+    explicit StorageController(u32 hardware_relative_controller_id);
+
+private:
+    u32 const m_controller_id { 0 };
+
+    u32 const m_hardware_relative_controller_id { 0 };
+};
+}