net/sched: Export tc_tunnel_key so its UAPI accessible

Export tc_tunnel_key so it can be used from user space.
Signed-off-by: NRoi Dayan <roid@mellanox.com>
Reviewed-by: NAmir Vadai <amir@vadai.me>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/uapi/linux/tc_act/Kbuild

@@ -11,3 +11,4 @@ header-y += tc_vlan.h
 header-y += tc_bpf.h
 header-y += tc_connmark.h
 header-y += tc_ife.h
+header-y += tc_tunnel_key.h