rtc: fix RTC removal

Since the rtc_register_device, removing an RTC device will end with a
refcount_t: underflow; use-after-free warning since put_device is called
twice in the device tear down path.

Fixes: fdcfd854333b ("rtc: rework rtc_register_device() resource management")
Signed-off-by: Alexandre Belloni <[e-mail]>
Reviewed-by: Bartosz Golaszewski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/rtc/class.c

···
 	cdev_device_del(&rtc->char_dev, &rtc->dev);
 	rtc->ops = NULL;
 	mutex_unlock(&rtc->ops_lock);
-	put_device(&rtc->dev);
 }
 
 static void devm_rtc_release_device(void *res)