net: sched: select cls when cls_act is enabled

It really makes no sense to have cls_act enabled without cls. In that
case, the cls_act code is dead. So select it.

This also fixes an issue recently reported by kbuild robot:
[linux-next:master 1326/4151] net/sched/act_api.c:37:18: error: implicit declaration of function 'tcf_chain_get'

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Fixes: db50514f ("net: sched: add termination action to allow goto chain")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>