rtc: switch to using is_visible() to control sysfs attributes

Instead of creating wakealarm attribute manually, after the device has been
registered, let's rely on facilities provided by the attribute groups to
control which attributes are visible and which are not. This allows to
create all needed attributes at once, at the same time that we register RTC
class device.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
diff --git a/drivers/rtc/rtc-core.h b/drivers/rtc/rtc-core.h
index 5f9df74..a098aea 100644
--- a/drivers/rtc/rtc-core.h
+++ b/drivers/rtc/rtc-core.h
@@ -48,23 +48,10 @@
 #endif
 
 #ifdef CONFIG_RTC_INTF_SYSFS
-
-extern void __init rtc_sysfs_init(struct class *);
-extern void rtc_sysfs_add_device(struct rtc_device *rtc);
-extern void rtc_sysfs_del_device(struct rtc_device *rtc);
-
+const struct attribute_group **rtc_get_dev_attribute_groups(void);
 #else
-
-static inline void rtc_sysfs_init(struct class *rtc)
+static inline const struct attribute_group **rtc_get_dev_attribute_groups(void)
 {
+	return NULL;
 }
-
-static inline void rtc_sysfs_add_device(struct rtc_device *rtc)
-{
-}
-
-static inline void rtc_sysfs_del_device(struct rtc_device *rtc)
-{
-}
-
 #endif