Don't require all drivers to use virtio_net_hdr

Don't require all drivers to use virtio_net_hdr

Hi Avi,

Thanks for catching the build error in this one.

Here's a new (yet uglier) version; the rest remain the same.

Cheers,
Mark.

Subject: [PATCH 08/11] kvm: qemu: Don't require all drivers to use virtio_net_hdr

The virtio-net driver is the only one which wishes to deal
with virtio_net_hdr headers, so add a "using_vnet_hdr" flag
to allow it to indicate this.

Preferably, we'd prefer to only enable IFF_VNET_HDR when
we're using virtio-net, but qemu's various abstractions
would make this very messy.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>