drivers/video/backlight/adp8860_bl.c: check strict_strtoul() return value

Handle return value, strict_strtoul is declared with attribute
warn_unused_result.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Acked-by: Richard Purdie <rpurdie@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/backlight/adp8860_bl.c

@@ -502,8 +502,10 @@ static ssize_t adp8860_bl_l1_daylight_max_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
 	struct adp8860_bl *data = dev_get_drvdata(dev);
+	int ret = strict_strtoul(buf, 10, &data->cached_daylight_max);
+	if (ret)
+		return ret;
 
-	strict_strtoul(buf, 10, &data->cached_daylight_max);
 	return adp8860_store(dev, buf, count, ADP8860_BLMX1);
 }
 static DEVICE_ATTR(l1_daylight_max, 0664, adp8860_bl_l1_daylight_max_show,