x86/PCI: Expose VMD's pci_dev in struct pci_sysdata

Expose VMD's pci_dev pointer in struct pci_sysdata.  This will be used
indirectly by intel-iommu.c to find the correct domain.

Link: https://lore.kernel.org/r/1579613871-301529-3-git-send-email-jonathan.derrick@intel.com


[bhelgaas: commit log]
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Christoph Hellwig <hch@lst.de>