serial: 8250: Clear dma tx_err unconditionally

No need to check non-zeroness first and then clear. Just set to zero
unconditionally.
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/3b885e7f-1372-3aa9-febd-34566ba25e3d@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dma.c

@@ -107,8 +107,7 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 
 	dma_async_issue_pending(dma->txchan);
 	serial8250_clear_THRI(p);
-	if (dma->tx_err)
-		dma->tx_err = 0;
+	dma->tx_err = 0;
 
 	return 0;
 err: