IB/mlx4: Add mechanism to support flow steering over IB links

The mlx4 device requires adding IB flow spec to rules that apply over
infiniband link layer.  This patch adds a mechanism to add such a rule.

If higher levels e.g. IP/UDP/TCP flow specs are provided, the device
requires us to add an empty wild-carded IB rule. Furthermore, the device
requires the QPN to be put in the rule.

Add here specific parsing support for IB empty rules and the ability
to self-generate missing specs based on existing ones.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>