Generalize flow_action_entry cleanup by extending the structure with
pointer to destructor function. Set the destructor in
tc_setup_flow_action(). Refactor tc_cleanup_flow_action() to call
entry->destructor() instead of using switch that dispatches by entry->id
and manually executes cleanup.

This refactoring is necessary for following patches in this series that
require destructor to use tc_action->ops callbacks that can't be easily
obtained in tc_cleanup_flow_action().
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>