vfio: Ignore -ENODEV when getting MSI cookie

When we try to get an MSI cookie for a VFIO device, that can fail if
CONFIG_IOMMU_DMA is not set. In this case iommu_get_msi_cookie() returns
-ENODEV, and that should not be fatal.

Ignore that case and proceed with the initialisation.

This fixes VFIO with a platform device on the Calxeda Midway (no MSIs).

Fixes: f6810c15 ("iommu/arm-smmu: Clean up early-probing workarounds")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>