rtc: rtc-tile: add missing platform_device_unregister() when module exit

We have registered platform device when module init, and
need unregister it when module exit.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

drivers/rtc/rtc-tile.c

diff --git a/drivers/rtc/rtc-tile.c b/drivers/rtc/rtc-tile.c
index 62db484..35dc926 100644
--- a/drivers/rtc/rtc-tile.c
+++ b/drivers/rtc/rtc-tile.c
@@ -151,6 +151,7 @@
  */
 static void __exit tile_rtc_driver_exit(void)
 {
+	platform_device_unregister(tile_rtc_platform_device);
 	platform_driver_unregister(&tile_rtc_platform_driver);
 }