net/mlx5: E-Switch, Add API to configure rules for the offloaded mode

This allows for upper levels in the driver, e.g the TC offload code to add
e-switch offloaded steering rules. The caller provides the rule spec for
matching, action, source and destination vports.

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>