serial: sprd: Fix a copy-paste err in sprd_request_dma()

when dma_request_chan rx_dma fails, dev_err log should print rx_dma
err log.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sprd_serial.c

@@ -506,7 +506,7 @@ static void sprd_request_dma(struct uart_port *port)
 	sp->rx_dma.chn = dma_request_chan(port->dev, "rx");
 	if (IS_ERR(sp->rx_dma.chn)) {
 		dev_err(port->dev, "request RX DMA channel failed, ret = %ld\n",
-			PTR_ERR(sp->tx_dma.chn));
+			PTR_ERR(sp->rx_dma.chn));
 		sp->rx_dma.enable = false;
 	}
 }