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/gdrom.c b/drivers/cdrom/gdrom.c
index 4e2bbcc..71ec426 100644
--- a/drivers/cdrom/gdrom.c
+++ b/drivers/cdrom/gdrom.c
@@ -827,7 +827,9 @@
 	del_gendisk(gd.disk);
 	if (gdrom_major)
 		unregister_blkdev(gdrom_major, GDROM_DEV_NAME);
-	return unregister_cdrom(gd.cd_info);
+	unregister_cdrom(gd.cd_info);
+
+	return 0;
 }
 
 static struct platform_driver gdrom_driver = {