enable virtio_net to return bus_info in ethtool -i consistent with emulated NICs

Add a new .bus_name to virtio_config_ops then modify virtio_net to
call through to it in an ethtool .get_drvinfo routine to report
bus_info in ethtool -i output which is consistent with other
emulated NICs and the output of lspci.

Signed-off-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index acc5e43..2f57380 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -361,7 +361,12 @@
 	return 0;
 }
 
+static const char *vm_bus_name(struct virtio_device *vdev)
+{
+	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
 
+	return vm_dev->pdev->name;
+}
 
 static struct virtio_config_ops virtio_mmio_config_ops = {
 	.get		= vm_get,
@@ -373,6 +378,7 @@
 	.del_vqs	= vm_del_vqs,
 	.get_features	= vm_get_features,
 	.finalize_features = vm_finalize_features,
+	.bus_name	= vm_bus_name,
 };