leds: wm831x: add missing const

Fixed the checkpatch warning as below:

  WARNING: static const char * array should probably be static const char * const
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>

drivers/leds/leds-wm831x-status.c

@@ -157,7 +157,7 @@ static int wm831x_status_blink_set(struct led_classdev *led_cdev,
 	return ret;
 }
 
-static const char *led_src_texts[] = {
+static const char * const led_src_texts[] = {
 	"otp",
 	"power",
 	"charger",