net/mlx5: Don't use termination tables in slow path

Don't use termination tables for packets that are steered to the slow path,
as a pre-step for supporting packet encap (packet reformat) action on
termination tables. Packet encap (reformat action) actions steer the packet
to the slow path until outer arp entries are resolved.

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