Kernel/Graphics: Don't try to enumerate PCI adapters if PCI is disabled

If there's no PCI bus, then it's safe to assume that the x86 machine we
run on supports VGA text mode console output with an ISA VGA adapter.
If this is the case, we just instantiate a ISAVGAAdapter object that
assumes this situation and allows us to boot into VGA text mode console.

Kernel/Graphics/VGA/PCIAdapter.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Types.h>
+#include <Kernel/Bus/PCI/Device.h>
+#include <Kernel/Graphics/Console/Console.h>
+#include <Kernel/Graphics/FramebufferDevice.h>
+#include <Kernel/Graphics/GenericGraphicsAdapter.h>
+#include <Kernel/PhysicalAddress.h>
+
+namespace Kernel {
+
+class PCIVGACompatibleAdapter : public VGACompatibleAdapter
+    , public PCI::Device {
+public:
+    static NonnullRefPtr<PCIVGACompatibleAdapter> initialize_with_preset_resolution(PCI::DeviceIdentifier const&, PhysicalAddress, size_t framebuffer_width, size_t framebuffer_height, size_t framebuffer_pitch);
+    static NonnullRefPtr<PCIVGACompatibleAdapter> initialize(PCI::DeviceIdentifier const&);
+
+    virtual bool framebuffer_devices_initialized() const override { return !m_framebuffer_device.is_null(); }
+
+protected:
+    explicit PCIVGACompatibleAdapter(PCI::Address);
+
+private:
+    PCIVGACompatibleAdapter(PCI::Address, PhysicalAddress, size_t framebuffer_width, size_t framebuffer_height, size_t framebuffer_pitch);
+
+    // ^GenericGraphicsAdapter
+    virtual void initialize_framebuffer_devices() override;
+
+    virtual void enable_consoles() override;
+    virtual void disable_consoles() override;
+
+protected:
+    PhysicalAddress m_framebuffer_address;
+    size_t m_framebuffer_width { 0 };
+    size_t m_framebuffer_height { 0 };
+    size_t m_framebuffer_pitch { 0 };
+
+    RefPtr<FramebufferDevice> m_framebuffer_device;
+};
+}