thermal: core: Constify static attribute_group structs

The only usage of these structs is to assign their address to the
thermal_zone_attribute_groups array, which consists of pointers to
const, so make them const to allow the compiler to put them in read-only
memory.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201128234342.36684-1-rikard.falkeborn@gmail.com

drivers/thermal/thermal_sysfs.c

@@ -425,7 +425,7 @@ static struct attribute *thermal_zone_dev_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group thermal_zone_attribute_group = {
+static const struct attribute_group thermal_zone_attribute_group = {
 	.attrs = thermal_zone_dev_attrs,
 };
 
@@ -434,7 +434,7 @@ static struct attribute *thermal_zone_mode_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group thermal_zone_mode_attribute_group = {
+static const struct attribute_group thermal_zone_mode_attribute_group = {
 	.attrs = thermal_zone_mode_attrs,
 };
 
@@ -468,7 +468,7 @@ static umode_t thermal_zone_passive_is_visible(struct kobject *kobj,
 	return 0;
 }
 
-static struct attribute_group thermal_zone_passive_attribute_group = {
+static const struct attribute_group thermal_zone_passive_attribute_group = {
 	.attrs = thermal_zone_passive_attrs,
 	.is_visible = thermal_zone_passive_is_visible,
 };