net: sched: use tcf_exts_has_actions instead of exts->nr_actions

For check in tcf_exts_dump use tcf_exts_has_actions helper instead
of exts->nr_actions for checking if there are any actions present.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>