Merge branch 'virtio_net-build_skb-fixes'

Xuan Zhuo says:

====================
virtio-net: fix for build_skb()

The logic of this piece is really messy. Fortunately, my refactored patch can be
completed with a small amount of testing.
====================

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>