block: Remove redundant 'return' statement

Remove redundant 'return' statement for 'void' functions.
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

@@ -3405,7 +3405,7 @@ static int __init ioc_init(void)
 
 static void __exit ioc_exit(void)
 {
-	return blkcg_policy_unregister(&blkcg_policy_iocost);
+	blkcg_policy_unregister(&blkcg_policy_iocost);
 }
 
 module_init(ioc_init);

block/blk-iolatency.c

@@ -1046,7 +1046,7 @@ static int __init iolatency_init(void)
 
 static void __exit iolatency_exit(void)
 {
-	return blkcg_policy_unregister(&blkcg_policy_iolatency);
+	blkcg_policy_unregister(&blkcg_policy_iolatency);
 }
 
 module_init(iolatency_init);