iommu/amd: Initialize dma_ops for hotplug and sriov devices

iommu/amd: Initialize dma_ops for hotplug and sriov devices

commit ac1534a55d1e87d59a21c09c570605933b551480 upstream.

When a device is added to the system at runtime the AMD
IOMMU driver initializes the necessary data structures to
handle translation for it. But it forgets to change the
per-device dma_ops to point to the AMD IOMMU driver. So
mapping actually never happens and all DMA accesses end in
an IO_PAGE_FAULT. Fix this.

Reported-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
[bwh: Backported to 3.2:
 - Adjust context
 - Use global iommu_pass_through; there is no per-device pass_through]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>