power: supply: move power_supply_attr_groups definition back to sysfs

As reported by the kernel test robot, 'power_supply_attr_group' is defined
but not used when CONFIG_SYSFS is not set. Sebastian suggested that the
correct fix implemented by this patch, instead of my attempt in commit
ea4367c4 ("power: supply: core: move power_supply_attr_group into #ifdef
block"), is to define power_supply_attr_groups in power_supply_sysfs.c and
expose it in the power_supply.h header. For the case where CONFIG_SYSFS=n,
define it as NULL.
Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Fixes: ea4367c4 ("power: supply: core: move power_supply_attr_group into #ifdef block")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202403021518.SUQzk3oA-lkp@intel.com/Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240303-class_cleanup-power-v2-1-e248b7128519@marliere.netSigned-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/power_supply.h

@@ -17,12 +17,12 @@ struct power_supply;
 
 extern void power_supply_init_attrs(void);
 extern int power_supply_uevent(const struct device *dev, struct kobj_uevent_env *env);
-extern const struct attribute_group power_supply_attr_group;
+extern const struct attribute_group *power_supply_attr_groups[];
 
 #else
 
 static inline void power_supply_init_attrs(void) {}
-static const struct attribute_group power_supply_attr_group;
+#define power_supply_attr_groups NULL
 #define power_supply_uevent NULL
 
 #endif /* CONFIG_SYSFS */

drivers/power/supply/power_supply_core.c

@@ -32,7 +32,6 @@ static const struct class power_supply_class = {
 
 static BLOCKING_NOTIFIER_HEAD(power_supply_notifier);
 
-__ATTRIBUTE_GROUPS(power_supply_attr);
 static const struct device_type power_supply_dev_type = {
 	.name = "power_supply",
 	.groups = power_supply_attr_groups,

drivers/power/supply/power_supply_sysfs.c

@@ -389,11 +389,16 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,
 	return 0;
 }
 
-const struct attribute_group power_supply_attr_group = {
+static const struct attribute_group power_supply_attr_group = {
 	.attrs = __power_supply_attrs,
 	.is_visible = power_supply_attr_is_visible,
 };
 
+const struct attribute_group *power_supply_attr_groups[] = {
+	&power_supply_attr_group,
+	NULL
+};
+
 void power_supply_init_attrs(void)
 {
 	int i;