This fix solves multiple Smatch static checker uninitialized errors:

drivers/virtio/virtio_ring.c:1516 virtqueue_add_packed()
error: uninitialized symbol 'prev'.

drivers/virtio/virtio_ring.c:1524 virtqueue_add_packed()
error: uninitialized symbol 'head_flags'.

drivers/virtio/virtio_ring.c:645 virtqueue_add_split()
error: uninitialized symbol 'prev'.

Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
---
 drivers/virtio/virtio_ring.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index be7309b1e860..001ea503d52c 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -553,7 +553,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq,
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	struct scatterlist *sg;
 	struct vring_desc *desc;
-	unsigned int i, n, avail, descs_used, prev, err_idx;
+	unsigned int i, n, avail, descs_used, prev = 0, err_idx;
 	int head;
 	bool indirect;
 
@@ -1411,8 +1411,8 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	struct vring_packed_desc *desc;
 	struct scatterlist *sg;
 	unsigned int i, n, c, descs_used, err_idx;
-	__le16 head_flags, flags;
-	u16 head, id, prev, curr, avail_used_flags;
+	__le16 head_flags = 0, flags;
+	u16 head, id, prev = 0, curr, avail_used_flags;
 	int err;
 
 	START_USE(vq);
-- 
2.43.0