vdo: omit need_resched() before cond_resched()

There's no need to call need_resched() because cond_resched() will do
nothing if need_resched() returns false.

Reviewed-by: Matthew Sakai <[e-mail]>
Signed-off-by: Mikulas Patocka <[e-mail]>

drivers/md/dm-vdo/funnel-workqueue.c

···
 		 * This speeds up some performance tests; that "other work" might include other VDO
 		 * threads.
 		 */
-		if (need_resched())
-			cond_resched();
+		cond_resched();
 	}
 
 	run_finish_hook(queue);