iommu/vt-d: Use Real PCI DMA device for IRTE

iommu/vt-d: Use Real PCI DMA device for IRTE

VMD retransmits child device MSI-X with the VMD endpoint's requester-id.
In order to support direct interrupt remapping of VMD child devices,
ensure that the IRTE is programmed with the VMD endpoint's requester-id
using pci_real_dma_dev().

Link: https://lore.kernel.org/r/20210210161315.316097-2-jonathan.derrick@intel.com
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Joerg Roedel <jroedel@suse.de>