AMD IOMMU: save pci_dev instead of devid

We need the pci_dev later anyways to enable MSI for the IOMMU hardware.
So remove the devid pointing to the BDF and replace it with the pci_dev
structure where the IOMMU is implemented.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>