FROMGIT: kfence: use power-efficient work queue to run delayed work

Use the power-efficient work queue, to avoid the pathological case where
we keep pinning ourselves on the same possibly idle CPU on systems that
want to be power-efficient (https://lwn.net/Articles/731052/).

Link: https://lkml.kernel.org/r/20210421105132.3965998-4-elver@google.com


Signed-off-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Jann Horn <jannh@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

Bug: 172317151
Bug: 185280916
Test: power team confirmed there's no regression
(cherry picked from commit e5bcc059aa2321383325e98628d65258bdcb306f
 https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

 akpm)
Signed-off-by: Alexander Potapenko <glider@google.com>
Change-Id: I53a2869987cdac165840e3878ff73735a03438fa