[PATCH] create_workqueue_thread() signedness fix

With "-W -Wno-unused -Wno-sign-compare" I get the following compile warning:

  CC      kernel/workqueue.o
kernel/workqueue.c: In function `workqueue_cpu_callback':
kernel/workqueue.c:504: warning: ordered comparison of pointer with integer zero

On error create_workqueue_thread() returns NULL, not negative pointer, so
following trivial patch suggests itself.
Signed-off-by: Mika Kukkonen <mikukkon@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/workqueue.c

@@ -499,7 +499,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
 	case CPU_UP_PREPARE:
 		/* Create a new workqueue thread for it. */
 		list_for_each_entry(wq, &workqueues, list) {
-			if (create_workqueue_thread(wq, hotcpu) < 0) {
+			if (!create_workqueue_thread(wq, hotcpu)) {
 				printk("workqueue for %i failed\n", hotcpu);
 				return NOTIFY_BAD;
 			}