leds: trigger: gpio: Convert to use kstrtox()

sscanf() is a heavy one and moreover requires additional boundary checks.
Convert driver to use kstrtou8() in gpio_trig_inverted_store().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20231103195310.948327-2-andriy.shevchenko@linux.intel.comSigned-off-by: Lee Jones <lee@kernel.org>

drivers/leds/trigger/ledtrig-gpio.c

@@ -53,14 +53,12 @@ static ssize_t gpio_trig_brightness_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t n)
 {
 	struct gpio_trig_data *gpio_data = led_trigger_get_drvdata(dev);
-	unsigned desired_brightness;
+	u8 desired_brightness;
 	int ret;
 
-	ret = sscanf(buf, "%u", &desired_brightness);
-	if (ret < 1 || desired_brightness > 255) {
-		dev_err(dev, "invalid value\n");
-		return -EINVAL;
-	}
+	ret = kstrtou8(buf, 10, &desired_brightness);
+	if (ret)
+		return ret;
 
 	gpio_data->desired_brightness = desired_brightness;