iommu/virtio: Add missing MODULE_DEVICE_TABLE

iommu/virtio: Add missing MODULE_DEVICE_TABLE

This patch adds missing MODULE_DEVICE_TABLE definition which generates
correct modalias for automatic loading of this driver when it is built
as an external module.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Bixuan Cui <cuibixuan@huawei.com>
Fixes: fa4afd78ea12 ("iommu/virtio: Build virtio-iommu as module")
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Link: https://lore.kernel.org/r/20210508031451.53493-1-cuibixuan@huawei.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>