net/tap: add eBPF API

net/tap: add eBPF API

This commit include BPF API to be used by TAP.

tap_flow_bpf_cls_q() - download to kernel BPF program that classifies
packets to their matching queues
tap_flow_bpf_calc_l3_l4_hash() - download to kernel BPF program that
calculates per packet layer 3 and layer 4 RSS hash
tap_flow_bpf_rss_map_create() - create BPF RSS map for storing RSS
parameters per RSS rule
tap_flow_bpf_update_rss_elem() - update BPF map entry with RSS rule
parameters

Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
Acked-by: Pascal Mazon <pascal.mazon@6wind.com>