net/mlx5e: Add support for offloading traffic from uplink to uplink

Termination tables change the direction of a packet in hw from RX to SX
pipeline. Use that to offload hairpin flows received from uplink and
sent back to uplink.

Currently termination tables are used for pushing VLAN to packets
received from uplink and targeting a VF. Extend the implementation to
allow forwarding packets to uplink. These packets can either be
encapsulated or not.

In case encapsulation is needed before forwarding, move the reformat
object to the termination table as required.

Extend the hash table key to include tunnel information for the sake of
reusing reformat objects.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>