net: make tap_receive() re-use tap_receive_iov() code In future we will want to prepend a virtio_net header if the NIC didn't supply one but IFF_VNET_HDR is enabled on the interface. This is most easily achived by using writev() in all cases. Signed-off-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>