workqueue: remove keventd_up()

keventd_up() no longer has in-kernel users.  Remove it and make
wq_online static.

Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 15d0811..ad0cd43 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -290,7 +290,7 @@
 static bool wq_power_efficient = IS_ENABLED(CONFIG_WQ_POWER_EFFICIENT_DEFAULT);
 module_param_named(power_efficient, wq_power_efficient, bool, 0444);
 
-bool wq_online;				/* can kworkers be created yet? */
+static bool wq_online;			/* can kworkers be created yet? */
 
 static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */