A customer using nohz_full has experienced the following interruption:

oslat-1004510 [018] timer_cancel:         timer=0xffff90a7ca663cf8
oslat-1004510 [018] timer_expire_entry:   timer=0xffff90a7ca663cf8 function=delayed_work_timer_fn now=4709188240 baseclk=4709188240
oslat-1004510 [018] workqueue_queue_work: work struct=0xffff90a7ca663cd8 function=fb_flashcursor workqueue=events_power_efficient req_cpu=8192 cpu=18
oslat-1004510 [018] workqueue_activate_work: work struct 0xffff90a7ca663cd8
oslat-1004510 [018] sched_wakeup:         kworker/18:1:326 [120] CPU:018
oslat-1004510 [018] timer_expire_exit:    timer=0xffff90a7ca663cf8
oslat-1004510 [018] irq_work_entry:       vector=246
oslat-1004510 [018] irq_work_exit:        vector=246
oslat-1004510 [018] tick_stop:            success=0 dependency=SCHED
oslat-1004510 [018] hrtimer_start:        hrtimer=0xffff90a70009cb00 function=tick_sched_timer/0x0 ...
oslat-1004510 [018] softirq_exit:         vec=1 [action=TIMER]
oslat-1004510 [018] softirq_entry:        vec=7 [action=SCHED]
oslat-1004510 [018] softirq_exit:         vec=7 [action=SCHED]
oslat-1004510 [018] tick_stop:            success=0 dependency=SCHED
oslat-1004510 [018] sched_switch:         oslat:1004510 [120] R ==> kworker/18:1:326 [120]
kworker/18:1-326 [018] workqueue_execute_start: work struct 0xffff90a7ca663cd8: function fb_flashcursor
kworker/18:1-326 [018] workqueue_queue_work: work struct=0xffff9078f119eed0 function=drm_fb_helper_damage_work workqueue=events req_cpu=8192 cpu=18
kworker/18:1-326 [018] workqueue_activate_work: work struct 0xffff9078f119eed0
kworker/18:1-326 [018] timer_start:          timer=0xffff90a7ca663cf8 function=delayed_work_timer_fn ...

Set wq_power_efficient to true, in case nohz_full is enabled.
This makes the power efficient workqueue be unbounded, which allows
workqueue items there to be moved to HK CPUs.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>