debugobj, workqueue: remove keventd_up() usage

Now that workqueue can handle work item queueing from very early
during boot, there is no need to gate schedule_work() while
!keventd_up().  Remove it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>