power: supply: ds2780: Switch to using the new API kobj_to_dev()

fixed the following coccicheck:
drivers/power/supply/ds2780_battery.c:627:60-61: WARNING opportunity for
kobj_to_dev()
drivers/power/supply/ds2780_battery.c:672:60-61: WARNING opportunity for
kobj_to_dev()
drivers/power/supply/ds2780_battery.c:640:60-61: WARNING opportunity for
kobj_to_dev()
drivers/power/supply/ds2780_battery.c:685:60-61: WARNING opportunity for
kobj_to_dev()

Signed-off-by: Tian Tao <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/ds2780_battery.c

···
 				struct bin_attribute *bin_attr,
 				char *buf, loff_t off, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct power_supply *psy = to_power_supply(dev);
 	struct ds2780_device_info *dev_info = to_ds2780_device_info(psy);
 
···
 				struct bin_attribute *bin_attr,
 				char *buf, loff_t off, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct power_supply *psy = to_power_supply(dev);
 	struct ds2780_device_info *dev_info = to_ds2780_device_info(psy);
 	int ret;
···
 				struct bin_attribute *bin_attr,
 				char *buf, loff_t off, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct power_supply *psy = to_power_supply(dev);
 	struct ds2780_device_info *dev_info = to_ds2780_device_info(psy);
 
···
 				struct bin_attribute *bin_attr,
 				char *buf, loff_t off, size_t count)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct power_supply *psy = to_power_supply(dev);
 	struct ds2780_device_info *dev_info = to_ds2780_device_info(psy);
 	int ret;