net/mlx5: Bridge, handle FDB events

Hardware supported by mlx5 driver doesn't provide learning and requires the
driver to emulate all switch-like behavior in software. As such, all
packets by default go through miss path, appear on representor and get to
software bridge, if it is the upper device of the representor. This causes
bridge to process packet in software, learn the MAC address to FDB and send
SWITCHDEV_FDB_ADD_TO_DEVICE event to all subscribers.

In order to offload FDB entries in mlx5, register switchdev notifier
callback and implement support for both 'added_by_user' and dynamic FDB
entry SWITCHDEV_FDB_ADD_TO_DEVICE events asynchronously using new
mlx5_esw_bridge_offloads->wq ordered workqueue. In workqueue callback
offload the ingress rule (matching FDB entry MAC as packet source MAC) and
egress table rule (matching FDB entry MAC as destination MAC). For ingress
table rule also match source vport to ensure that only traffic coming from
expected bridge port is matched by offloaded rule. Save all the relevant
FDB entry data in struct mlx5_esw_bridge_fdb_entry instance and insert the
instance in new mlx5_esw_bridge->fdb_list list (for traversing all entries
by software ageing implementation in following patch) and in new
mlx5_esw_bridge->fdb_ht hash table for fast retrieval. Notify the bridge
that FDB entry has been offloaded by sending SWITCHDEV_FDB_OFFLOADED
notification.

Delete FDB entry on reception of SWITCHDEV_FDB_DEL_TO_DEVICE event.

Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Jianbo Liu <jianbol@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>