iommu/amd: Remove calc_devid() and use PCI_DEVID() from PCI

Change to remove calc_devid() and use PCI_DEVID() from PCI instead.

Signed-off-by: Shuah Khan <shuah.khan@hp.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Joerg Roedel <joro@8bytes.org>