memory: Add Error** argument to memory_get_xlat_addr()

memory: Add Error** argument to memory_get_xlat_addr()

Let the callers do the reporting. This will be useful in
vfio_iommu_map_dirty_notify().

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>