iommu/vt-d: Make device_to_iommu() cope with non-PCI devices

Pass the struct device to it, and also make it return the bus/devfn to use,
since that is also stored in the DMAR table.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --cc drivers/iommu/intel-iommu.c
Simple merge