serial: sh-sci: Don't check for mctrl_gpio_to_gpiod() returning error

Since commit 1d267ea6 ("serial: mctrl-gpio: simplify init
routine"), mctrl_gpio_init() returns failure if the assignment to any
member of the gpio array results in an error pointer.
Since commit c359522194593815 ("serial: mctrl_gpio: Avoid probe failures
in case of missing gpiolib"), mctrl_gpio_to_gpiod() returns NULL in the
!CONFIG_GPIOLIB case.
Hence there is no longer a need to check for mctrl_gpio_to_gpiod()
returning an error value.  A simple NULL check is sufficient.

This follows the spirit of commit 445df7ff ("serial: mctrl-gpio:
drop usages of IS_ERR_OR_NULL") in the mctrl-gpio core.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20190814092924.13857-4-geert+renesas@glider.beSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sh-sci.c

@@ -2099,12 +2099,12 @@ static unsigned int sci_get_mctrl(struct uart_port *port)
 	if (s->autorts) {
 		if (sci_get_cts(port))
 			mctrl |= TIOCM_CTS;
-	} else if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_CTS))) {
+	} else if (!mctrl_gpio_to_gpiod(gpios, UART_GPIO_CTS)) {
 		mctrl |= TIOCM_CTS;
 	}
-	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_DSR)))
+	if (!mctrl_gpio_to_gpiod(gpios, UART_GPIO_DSR))
 		mctrl |= TIOCM_DSR;
-	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(gpios, UART_GPIO_DCD)))
+	if (!mctrl_gpio_to_gpiod(gpios, UART_GPIO_DCD))
 		mctrl |= TIOCM_CAR;
 
 	return mctrl;
@@ -3285,10 +3285,8 @@ static int sci_probe_single(struct platform_device *dev,
 		return PTR_ERR(sciport->gpios);
 
 	if (sciport->has_rtscts) {
-		if (!IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(sciport->gpios,
-							UART_GPIO_CTS)) ||
-		    !IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(sciport->gpios,
-							UART_GPIO_RTS))) {
+		if (mctrl_gpio_to_gpiod(sciport->gpios, UART_GPIO_CTS) ||
+		    mctrl_gpio_to_gpiod(sciport->gpios, UART_GPIO_RTS)) {
 			dev_err(&dev->dev, "Conflicting RTS/CTS config\n");
 			return -EINVAL;
 		}