Kernel/PCI: Fix support of multiple PCI host controllers enumeration

First scan PCI bus 0. Find any device on that bus, and if it's a
PCI-to-PCI bridge, recursively scan it too.

Then try to handle Multiple PCI host bridges on slot 0, device 0.
If we happen to miss some PCI buses because they are not reachable
through recursive PCI-to-PCI bridges scanning starting from bus 0, we
might find them in this scanning.

Kernel/PCI/Access.h

@@ -6,6 +6,7 @@
 
 #pragma once
 
+#include <AK/Bitmap.h>
 #include <AK/String.h>
 #include <AK/Vector.h>
 #include <Kernel/PCI/Definitions.h>
@@ -49,6 +50,7 @@ protected:
     virtual ~Access() = default;
 
     Vector<PhysicalID> m_physical_ids;
+    Bitmap m_enumerated_buses;
 };
 
 }