leds: leds-lp5523: replace strict_strtoul() with kstrtoul()

The usage of strict_strtoul() is not preferred, because
strict_strtoul() is obsolete. Thus, kstrtoul() should be
used.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
index 4ddf7b4..59ec383 100644
--- a/drivers/leds/leds-lp5523.c
+++ b/drivers/leds/leds-lp5523.c
@@ -710,7 +710,7 @@
 	ssize_t ret;
 	unsigned long curr;
 
-	if (strict_strtoul(buf, 0, &curr))
+	if (kstrtoul(buf, 0, &curr))
 		return -EINVAL;
 
 	if (curr > led->max_current)