serial: 8250: Add helper for clearing IER

A number of places want to clear IER with the same CAP_UUE trick.
Create a helper for that.
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20220816120759.11552-1-ilpo.jarvinen@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_port.c

@@ -752,6 +752,14 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep)
 	serial8250_rpm_put(p);
 }
 
+static void serial8250_clear_IER(struct uart_8250_port *up)
+{
+	if (up->capabilities & UART_CAP_UUE)
+		serial_out(up, UART_IER, UART_IER_UUE);
+	else
+		serial_out(up, UART_IER, 0);
+}
+
 #ifdef CONFIG_SERIAL_8250_RSA
 /*
  * Attempts to turn on the RSA FIFO.  Returns zero on failure.
@@ -1329,10 +1337,7 @@ static void autoconfig(struct uart_8250_port *up)
 	serial8250_out_MCR(up, save_mcr);
 	serial8250_clear_fifos(up);
 	serial_in(up, UART_RX);
-	if (up->capabilities & UART_CAP_UUE)
-		serial_out(up, UART_IER, UART_IER_UUE);
-	else
-		serial_out(up, UART_IER, 0);
+	serial8250_clear_IER(up);
 
 out_unlock:
 	spin_unlock_irqrestore(&port->lock, flags);
@@ -2142,10 +2147,7 @@ static void serial8250_put_poll_char(struct uart_port *port,
 	 *	First save the IER then disable the interrupts
 	 */
 	ier = serial_port_in(port, UART_IER);
-	if (up->capabilities & UART_CAP_UUE)
-		serial_port_out(port, UART_IER, UART_IER_UUE);
-	else
-		serial_port_out(port, UART_IER, 0);
+	serial8250_clear_IER(up);
 
 	wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
 	/*
@@ -3383,11 +3385,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
 	 *	First save the IER then disable the interrupts
 	 */
 	ier = serial_port_in(port, UART_IER);
-
-	if (up->capabilities & UART_CAP_UUE)
-		serial_port_out(port, UART_IER, UART_IER_UUE);
-	else
-		serial_port_out(port, UART_IER, 0);
+	serial8250_clear_IER(up);
 
 	/* check scratch reg to see if port powered off during system sleep */
 	if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) {