netdev-vport: Make gre netdev type to use TC rules

The offload api functions already assigned to every tunnel class.
For gre tunnel class only need to also assign the get_ifindex function.

Signed-off-by: Eli Britstein <elibr@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>

lib/netdev-vport.c

@@ -1154,7 +1154,8 @@ netdev_vport_tunnel_register(void)
               .type = "gre",
               .build_header = netdev_gre_build_header,
               .push_header = netdev_gre_push_header,
-              .pop_header = netdev_gre_pop_header
+              .pop_header = netdev_gre_pop_header,
+              .get_ifindex = NETDEV_VPORT_GET_IFINDEX,
           },
           {{NULL, NULL, 0, 0}}
         },