rtc: dev: properly manage lifetime of dev and cdev in rtc device

struct rtc embeds both struct dev and struct cdev.  Unfortunately character
device structure may outlive the parent rtc structure unless we set it up
as parent of character device so that it will stay pinned until character
device is freed.
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: NKrzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: NAlexandre Belloni <alexandre.belloni@free-electrons.com>

drivers/rtc/rtc-dev.c

@@ -477,6 +477,7 @@ void rtc_dev_prepare(struct rtc_device *rtc)
 
 	cdev_init(&rtc->char_dev, &rtc_dev_fops);
 	rtc->char_dev.owner = rtc->owner;
+	rtc->char_dev.kobj.parent = &rtc->dev.kobj;
 }
 
 void rtc_dev_add_device(struct rtc_device *rtc)