PCIe root complex driver (driver model) and small cleanups

[andreiw]

 Ctrl[24] PCI(e) Root
   Ctrl[8E] DT(DtRoot)/DT(soc)/DT(pci@30000000)/Pci(0x0,0x0)
   Ctrl[8F] eXtensible Host Controller (USB 3.0)
     Ctrl[92] Generic Usb Keyboard
       Ctrl[67] Primary Console Input Device
   Ctrl[90] DT(DtRoot)/DT(soc)/DT(pci@30000000)/Pci(0x2,0x0)
   Ctrl[91] DT(DtRoot)/DT(soc)/DT(pci@30000000)/Pci(0x3,0x0)