net/mlx5: Eswitch, enable forwarding back to uplink port

Add dependencny on cap termination_table_raw_traffic to allow non
encapsulated packets received from uplink to be forwarded back to the
received uplink port.

Refactor the conditions into a separate function.

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