virtio: use dev_to_virtio wrapper in virtio

commit 9bffdca8c64a72ac54c47a552734ab457bc720d4 upstream.

Use dev_to_virtio wrapper in virtio to make code clearly.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc drivers/virtio/virtio.c
Simple merge

diff --cc include/linux/virtio.h
Simple merge