net/mlx5e: en_tc: Rely just on register loopback for tunnel restoration

Register loopback which is needed for tunnel restoration, is now always
enabled if supported and not just with metadata enabled, check for
that instead.

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Reviewed-by: Oz Shlomo <ozsh@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>