jffs2: use cond_resched() instead of yield()

yield() has different semantics meanwhile and even causes RT-kernels to
BUG. Replace the only appearance left in jffs2.

Signed-off-by: Wolfram Sang <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>

fs/jffs2/erase.c

···
 		}
 
 		/* Be nice */
-		yield();
+		cond_resched();
 		mutex_lock(&c->erase_free_sem);
 		spin_lock(&c->erase_completion_lock);
 	}