net/mlx5e: Add RSS support for hairpin

Support RSS for hairpin traffic. We create multiple hairpin RQ/SQ pairs
and RSS TTC table per hairpin instance and steer the related flows
through that table so they are spread between the pairs.

We open one pair per 50Gbs link speed, for all speeds <= 50Gbs, there
is one pair and no RSS while for 100Gbs ports two RSSed pairs.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>