leds: turris-omnia: fix checkpatch warning

Use kstrtoul instead of sscanf to satisfy checkpatch.

Signed-off-by: Marek Behún <[e-mail]>
Signed-off-by: Pavel Machek <[e-mail]>

drivers/leds/leds-turris-omnia.c

···
 {
 	struct i2c_client *client = to_i2c_client(dev);
 	struct omnia_leds *leds = i2c_get_clientdata(client);
-	unsigned int brightness;
+	unsigned long brightness;
 	int ret;
 
-	if (sscanf(buf, "%u", &brightness) != 1)
+	if (kstrtoul(buf, 10, &brightness))
 		return -EINVAL;
 
 	if (brightness > 100)