cris: fix a build error in sync_serial_open()

Fix:

  arch/cris/arch-v10/drivers/sync_serial.c:628: error: 'ret' undeclared (first use in this function)

'ret' should be 'err'.
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NWANG Cong <xiyou.wangcong@gmail.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/cris/arch-v10/drivers/sync_serial.c

@@ -625,11 +625,11 @@ static int sync_serial_open(struct inode *inode, struct file *file)
 			*R_IRQ_MASK1_SET = 1 << port->data_avail_bit;
 		DEBUG(printk(KERN_DEBUG "sser%d rec started\n", dev));
 	}
-	ret = 0;
+	err = 0;
 	
 out:
 	mutex_unlock(&sync_serial_mutex);
-	return ret;
+	return err;
 }
 
 static int sync_serial_release(struct inode *inode, struct file *file)