virtio: make config_ops const

It is just a table of function pointers, make it const for cleanliness and security
reasons.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 833e6db..1ba0d68 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -423,7 +423,7 @@
 	return vm_dev->pdev->name;
 }
 
-static struct virtio_config_ops virtio_mmio_config_ops = {
+static const struct virtio_config_ops virtio_mmio_config_ops = {
 	.get		= vm_get,
 	.set		= vm_set,
 	.get_status	= vm_get_status,