workqueue: clean up delayed_work initializers and add missing one

Reimplement delayed_work initializers using new timer initializers
which take timer flags.  This reduces code duplications and will ease
further initializer changes.  This patch also adds a missing
initializer - INIT_DEFERRABLE_WORK_ONSTACK().

Signed-off-by: Tejun Heo <tj@kernel.org>
1 file changed