fix the serial initialization issue

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@16 bbd45198-f89e-11dd-88c7-29a3b14d5316

libcpu/arm/stm32/serial.c

@@ -107,7 +107,7 @@ static rt_err_t rt_serial_init (rt_device_t dev)
 			rt_memset(uart->int_rx->rx_buffer, 0, 
 				sizeof(uart->int_rx->rx_buffer));
 			uart->int_rx->read_index = 0;
-                        uart->int_rx->read_index = 0;
+			uart->int_rx->save_index = 0;
 		}
 		
 		if (dev->flag & RT_DEVICE_FLAG_DMA_RX)