net/mlx4_en: Implement mcast loopback prevention for ETH qps

Set the mcast loopback prevention bit in the QPC for ETH MLX QPs (not
RSS QPs), when the firmware supports this feature. In addition, all rx
ring QPs need to be updated in order not to enforce loopback checks.
This prevents getting packets we sent both from the network stack and
the HCA. Loopback prevention is done by comparing the counter indices of
the sent and receiving QPs. If they're equal, packets aren't
loopback-ed.

Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>