iommu/virtio: Fix compile error with viommu_capable()

iommu/virtio: Fix compile error with viommu_capable()

A recent fix introduced viommu_capable() but other changes
from Robin change the function signature of the call-back it
is used for.

When both changes are merged a compile error will happen
because the function pointer types mismatch. Fix that by
updating the viommu_capable() signature after the merge.

Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20220907151154.21911-1-joro@8bytes.org