vdpa/mlx5: Set mkey modified flags on all VQs

Otherwise, when virtqueues are moved from INIT to READY the latest mkey
will not be set appropriately.

Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Message-Id: <20240626-stage-vdpa-vq-precreate-v2-14-560c491078df@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>