megaraid: fix BUG_ON() from incorrect use of delayed work

megaraid: fix BUG_ON() from incorrect use of delayed work

megaraid use INIT_WORK to declare a hotplug_work, but cast the
hotplug_work from work_struct to delayed_work and
schedule_delayed_work on it.  This is very dangerous, as other part of
delayed_work might be kernel memories allocated by others.

With commit 8852aac ("workqueue: mod_delayed_work_on() shouldn't queue
timer on 0 delay"), schedule_delayed_work() will check dwork->timer
before queue_work even when @delay is 0, this causes megaraid code to
hit the BUG_ON() in workqueue code.  Change megaraid code to use
delayed work.

Signed-off-by: Xiaotian Feng <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
Cc: Neela Syam Kolli <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: [email protected]