AMD/IOMMU: Fix passthrough following c/s d7cfeb7c13e

AMD/IOMMU: Fix passthrough following c/s d7cfeb7c13e

"AMD/IOMMU: don't blindly allocate interrupt remapping tables" introduces a
call at runtime from amd_iommu_add_device() to amd_iommu_set_intremap_table()
which is still marked as __init.

On one AMD Rome machine we have, this results in a crash the moment we try to
use an SR-IOV VF in a VM.

Reported-by: Jennifer Herbert <jennifer.herbert@citrix.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>