Kernel: Move VirtIO code into the Bus source folder

The VirtIO code handles functionality related to the VirtIO bus, so it
really should be in the Bus folder.

Kernel/Bus/VirtIO/VirtIORNG.h

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2021, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Bus/VirtIO/VirtIO.h>
+#include <Kernel/Devices/CharacterDevice.h>
+#include <Kernel/Random.h>
+
+namespace Kernel {
+
+#define REQUESTQ 0
+
+class VirtIORNG final : public CharacterDevice
+    , public VirtIODevice {
+public:
+    virtual StringView purpose() const override { return class_name(); }
+    virtual StringView class_name() const override { return m_class_name; }
+
+    virtual bool can_read(const FileDescription&, size_t) const override { return false; }
+    virtual KResultOr<size_t> read(FileDescription&, u64, UserOrKernelBuffer&, size_t) override { return 0; }
+    virtual bool can_write(const FileDescription&, size_t) const override { return false; }
+    virtual KResultOr<size_t> write(FileDescription&, u64, const UserOrKernelBuffer&, size_t) override { return 0; }
+
+    virtual mode_t required_mode() const override { return 0666; }
+    virtual String device_name() const override { return "hwrng"; }
+
+    VirtIORNG(PCI::Address);
+    virtual ~VirtIORNG() override;
+
+private:
+    virtual bool handle_device_config_change() override;
+    virtual void handle_queue_update(u16 queue_index) override;
+    void request_entropy_from_host();
+
+    OwnPtr<Memory::Region> m_entropy_buffer;
+    EntropySource m_entropy_source;
+};
+
+}