rtc: do not return void value

This patch fixes these sparse warnings:

drivers/rtc/rtc-ds1742.c:265:2: warning: returning void-valued expression
drivers/rtc/rtc-ds1553.c:409:2: warning: returning void-valued expression
Signed-off-by: NAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: David Brownell <david-b@pacbell.net>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-ds1553.c

@@ -407,7 +407,7 @@ static __init int ds1553_init(void)
 
 static __exit void ds1553_exit(void)
 {
-	return platform_driver_unregister(&ds1553_rtc_driver);
+	platform_driver_unregister(&ds1553_rtc_driver);
 }
 
 module_init(ds1553_init);

drivers/rtc/rtc-ds1742.c

@@ -263,7 +263,7 @@ static __init int ds1742_init(void)
 
 static __exit void ds1742_exit(void)
 {
-	return platform_driver_unregister(&ds1742_rtc_driver);
+	platform_driver_unregister(&ds1742_rtc_driver);
 }
 
 module_init(ds1742_init);