iommu/virtio: Enable x86 support

iommu/virtio: Enable x86 support

With the VIOT support in place, x86 platforms can now use the
virtio-iommu.

Because the other x86 IOMMU drivers aren't yet ready to use the
acpi_dma_setup() path, x86 doesn't implement arch_setup_dma_ops() at the
moment. Similarly to Vt-d and AMD IOMMU, clear the DMA ops and call
iommu_setup_dma_ops() from probe_finalize().

Acked-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20210618152059.1194210-6-jean-philippe@linaro.org
Signed-off-by: Joerg Roedel <jroedel@suse.de>