tty/serial: atmel: use true,false for bool variable

Fixes coccicheck warning:

drivers/tty/serial/atmel_serial.c:1062:1-23: WARNING: Assignment of 0/1 to bool variable
drivers/tty/serial/atmel_serial.c:1261:1-23: WARNING: Assignment of 0/1 to bool variable
drivers/tty/serial/atmel_serial.c:1688:3-25: WARNING: Assignment of 0/1 to bool variable
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zheng Bin <zhengbin13@huawei.com>
Link: https://lore.kernel.org/r/1578881777-65475-4-git-send-email-zhengbin13@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -1072,7 +1072,7 @@ static int atmel_prepare_tx_dma(struct uart_port *port)
 
 chan_err:
 	dev_err(port->dev, "TX channel not available, switch to pio\n");
-	atmel_port->use_dma_tx = 0;
+	atmel_port->use_dma_tx = false;
 	if (atmel_port->chan_tx)
 		atmel_release_tx_dma(port);
 	return -EINVAL;
@@ -1271,7 +1271,7 @@ static int atmel_prepare_rx_dma(struct uart_port *port)
 
 chan_err:
 	dev_err(port->dev, "RX channel not available, switch to pio\n");
-	atmel_port->use_dma_rx = 0;
+	atmel_port->use_dma_rx = false;
 	if (atmel_port->chan_rx)
 		atmel_release_rx_dma(port);
 	return -EINVAL;
@@ -1698,7 +1698,7 @@ static int atmel_prepare_rx_pdc(struct uart_port *port)
 					DMA_FROM_DEVICE);
 				kfree(atmel_port->pdc_rx[0].buf);
 			}
-			atmel_port->use_pdc_rx = 0;
+			atmel_port->use_pdc_rx = false;
 			return -ENOMEM;
 		}
 		pdc->dma_addr = dma_map_single(port->dev,