virtio.h uses struct module, add a forward declaration to
make the header self-contained.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/linux/virtio.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 132a474e5914..3626eb694728 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -13,6 +13,8 @@
 #include <linux/completion.h>
 #include <linux/virtio_features.h>
 
+struct module;
+
 /**
  * struct virtqueue - a queue to register buffers for sending or receiving.
  * @list: the chain of virtqueues for this device
-- 
MST