intel-iommu: Don't set identity mapping for bypassed graphics devices

We should check iommu_dummy() _first_, because that means it's attached
to an iommu that we've just disabled completely. At the moment, we might
try to put the device into the identity mapping domain.

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

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