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/SD/SDMemoryCard.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2023, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/Result.h>
+#include <AK/Types.h>
+#include <Kernel/Devices/Storage/SD/Registers.h>
+#include <Kernel/Devices/Storage/StorageDevice.h>
+#include <Kernel/Locking/Mutex.h>
+
+namespace Kernel {
+
+class SDHostController;
+
+class SDMemoryCard : public StorageDevice {
+public:
+    SDMemoryCard(SDHostController& sdhc, StorageDevice::LUNAddress, u32 hardware_relative_controller_id, u32 block_len, u64 capacity_in_blocks, u32 relative_card_address, SD::OperatingConditionRegister ocr, SD::CardIdentificationRegister cid, SD::SDConfigurationRegister scr);
+
+    // ^StorageDevice
+    virtual CommandSet command_set() const override { return CommandSet::SD; }
+
+    // ^BlockDevice
+    virtual void start_request(AsyncBlockDeviceRequest&) override;
+
+private:
+    enum class CardAddressingMode {
+        ByteAddressing,
+        BlockAddressing
+    };
+    CardAddressingMode card_addressing_mode() const
+    {
+        return m_ocr.card_capacity_status ? CardAddressingMode::BlockAddressing : CardAddressingMode::ByteAddressing;
+    }
+
+    Mutex m_lock { "SDMemoryCard"sv };
+    SDHostController& m_sdhc;
+
+    u32 m_relative_card_address;
+    SD::OperatingConditionRegister m_ocr;
+    SD::CardIdentificationRegister m_cid;
+    SD::SDConfigurationRegister m_scr;
+};
+
+}