backlight: hx8357: Fix potential NULL pointer dereference

The "im" pins are optional. Add missing check in the hx8357_probe().

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/642e1230-3358-4006-a17f-3f297897ae74@moroto.mountain
Fixes: 7d84a63 ("backlight: hx8357: Convert to agnostic GPIO API")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20240114143921.550736-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/video/backlight/hx8357.c

@@ -609,11 +609,13 @@ static int hx8357_probe(struct spi_device *spi)
 	lcd->im_pins = devm_gpiod_get_array_optional(dev, "im", GPIOD_OUT_LOW);
 	if (IS_ERR(lcd->im_pins))
 		return dev_err_probe(dev, PTR_ERR(lcd->im_pins), "failed to request im GPIOs\n");
-	if (lcd->im_pins->ndescs < HX8357_NUM_IM_PINS)
-		return dev_err_probe(dev, -EINVAL, "not enough im GPIOs\n");
+	if (lcd->im_pins) {
+		if (lcd->im_pins->ndescs < HX8357_NUM_IM_PINS)
+			return dev_err_probe(dev, -EINVAL, "not enough im GPIOs\n");
 
-	for (i = 0; i < HX8357_NUM_IM_PINS; i++)
-		gpiod_set_consumer_name(lcd->im_pins->desc[i], "im_pins");
+		for (i = 0; i < HX8357_NUM_IM_PINS; i++)
+			gpiod_set_consumer_name(lcd->im_pins->desc[i], "im_pins");
+	}
 
 	lcdev = devm_lcd_device_register(&spi->dev, "mxsfb", &spi->dev, lcd,
 					&hx8357_ops);