sched: add helper for updating statistics on all actions

Forgetting to disable preemption around tcf_action_stats_update()
seems to be a common mistake.  Add a helper function for updating
stats on all actions of a filter.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>