veth: rely on veth_rq in veth_xdp_flush_bq signature

Substitute net_device point with veth_rq one in veth_xdp_flush_bq,
veth_xdp_flush and veth_xdp_tx signature. This is a preliminary patch
to account xdp_xmit counter on 'receiving' veth_rq

Acked-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>