cdrom: make unregister_cdrom() return void

Now unregister_cdrom() always returns 0.
Make it return void and update all callers that check the return value.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Cc: Borislav Petkov <petkovbb@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/cdrom/viocd.c b/drivers/cdrom/viocd.c
index cac06bc..b74b6c2 100644
--- a/drivers/cdrom/viocd.c
+++ b/drivers/cdrom/viocd.c
@@ -650,10 +650,7 @@
 {
 	struct disk_info *d = &viocd_diskinfo[vdev->unit_address];
 
-	if (unregister_cdrom(&d->viocd_info) != 0)
-		printk(VIOCD_KERN_WARNING
-				"Cannot unregister viocd CD-ROM %s!\n",
-				d->viocd_info.name);
+	unregister_cdrom(&d->viocd_info);
 	del_gendisk(d->viocd_disk);
 	blk_cleanup_queue(d->viocd_disk->queue);
 	put_disk(d->viocd_disk);