leds: blinkm: constify attribute_group structures.

attribute_group are not supposed to change at runtime. All functions
working with attribute_group provided by <linux/sysfs.h> work with
const attribute_group. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

drivers/leds/leds-blinkm.c

@@ -298,7 +298,7 @@ static struct attribute *blinkm_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group blinkm_group = {
+static const struct attribute_group blinkm_group = {
 	.name = "blinkm",
 	.attrs = blinkm_attrs,
 };