The virtio_net offload APIs are used on the NIC's peer (i.e. the tap
device). The API was defined to implicitly use nc->peer, saving the
caller the trouble.
This wasn't ideal because:
1. There are callers who have the peer but not the NIC. Currently they
are forced to bypass the API and access peer->info->... directly.
2. The rest of the net.h API uses nc, not nc->peer, so it is
inconsistent.
This patch pushes nc->peer back up to callers.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>