Linux maintains a list of all known PCI IDs for Intel GPUs. We need this list
in the future because the quirks applied by our GVT-d don't work for the latest
generation of Intels integrated graphcis devices. We have to detect the
generation and then apply some generation specific quirks to it. Fortunately,
Linux has macros for each graphic device type making it easy for us to use that
header to detect the generation of the device in the next step.