virtio_net: Remove BUG() to avoid machine dead

stable inclusion
from linux-4.19.198
commit 34218ccb387c1e5e94b2baa6e337fb0367edede0

--------------------------------

[ Upstream commit 85eb1389 ]

We should not directly BUG() when there is hdr error, it is
better to output a print when such error happens. Currently,
the caller of xmit_skb() already did it.
Signed-off-by: NXianting Tian <xianting.tian@linux.alibaba.com>
Reviewed-by: NLeon Romanovsky <leonro@nvidia.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/virtio_net.c

@@ -1536,7 +1536,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
 	if (virtio_net_hdr_from_skb(skb, &hdr->hdr,
 				    virtio_is_little_endian(vi->vdev), false,
 				    0))
-		BUG();
+		return -EPROTO;
 
 	if (vi->mergeable_rx_bufs)
 		hdr->num_buffers = 0;