net_sched: remove list_head from tc_action

After commit 90b73b77, list_head is no longer needed.
Now we just need to convert the list iteration to array
iteration for drivers.

Fixes: 90b73b77

 ("net: sched: change action API to use array of pointers to actions")
Cc: Jiri Pirko <jiri@mellanox.com>
Cc: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>