tty: serial: lpc32xx_hs: use serial_lpc32xx_stop_tx() helper

Instead of open-coding what serial_lpc32xx_stop_tx() already does, call
it in __serial_lpc32xx_tx() directly.

Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220224111028.20917-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/lpc32xx_hs.c

@@ -276,10 +276,11 @@ static void __serial_lpc32xx_rx(struct uart_port *port)
 	tty_flip_buffer_push(tport);
 }
 
+static void serial_lpc32xx_stop_tx(struct uart_port *port);
+
 static void __serial_lpc32xx_tx(struct uart_port *port)
 {
 	struct circ_buf *xmit = &port->state->xmit;
-	unsigned int tmp;
 
 	if (port->x_char) {
 		writel((u32)port->x_char, LPC32XX_HSUART_FIFO(port->membase));
@@ -306,11 +307,8 @@ static void __serial_lpc32xx_tx(struct uart_port *port)
 		uart_write_wakeup(port);
 
 exit_tx:
-	if (uart_circ_empty(xmit)) {
-		tmp = readl(LPC32XX_HSUART_CTRL(port->membase));
-		tmp &= ~LPC32XX_HSU_TX_INT_EN;
-		writel(tmp, LPC32XX_HSUART_CTRL(port->membase));
-	}
+	if (uart_circ_empty(xmit))
+		serial_lpc32xx_stop_tx(port);
 }
 
 static irqreturn_t serial_lpc32xx_interrupt(int irq, void *dev_id)