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 <w.sang@pengutronix.de>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

fs/jffs2/erase.c

@@ -151,7 +151,7 @@ int jffs2_erase_pending_blocks(struct jffs2_sb_info *c, int count)
 		}
 
 		/* Be nice */
-		yield();
+		cond_resched();
 		mutex_lock(&c->erase_free_sem);
 		spin_lock(&c->erase_completion_lock);
 	}