[RFC PATCH 2/2] tiny_rcu: resched when call_rcu_sched() on idle_task

For rcu_sched in UP, context-switch = QS = GP, thus we can force a context-switch when call_rcu_sched() is happened on idle_task. After doing so, rcu_idle/irq_enter/exit() are useless, so we can simply make these functions empty. More important, this change does not change the functionality

[RFC PATCH 2/2] tiny_rcu: resched when call_rcu_sched() on idle_task

For rcu_sched in UP, context-switch = QS = GP, thus we can force a context-switch when call_rcu_sched() is happened on idle_task. After doing so, rcu_idle/irq_enter/exit() are useless, so we can simply make these functions empty. More important, this change does not change the functionality