net: netsec: add XDP support

The interface only supports 1 Tx queue so locking is introduced on
the Tx queue if XDP is enabled to make sure .ndo_start_xmit and
.ndo_xdp_xmit won't corrupt Tx ring

- Performance (SMMU off)

Benchmark   XDP_SKB     XDP_DRV
xdp1        291kpps     344kpps
rxdrop      282kpps     342kpps

- Performance (SMMU on)
Benchmark   XDP_SKB     XDP_DRV
xdp1        167kpps     324kpps
rxdrop      164kpps     323kpps

Signed-off-by: Ilias Apalodimas <[email protected]>
Acked-by: Jesper Dangaard Brouer <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: apalos