Define one destination MAC address per DPDK queue

Description

Contrarily to mlx5 (ConnextX-3), mlx4 (ConnectX-4 and above) cannot filter on the source MAC address, only on the destination MAC address. Therefore, it is impossible to redirect different BE boards to different queues. Instead, one needs to send each BE data to different MAC addresses (even if on the same port).

Possible fixes

Use the MAC source address to identify the board, but not to redirect it into a specific queue. Use multiple MAC addresses instead (flow rules can be added on the fly, not queues).