[SCSI] sr: fix error handling in module_init

Sweep registered blkdev when scsi_register_driver has failed.

Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/sr.c

@@ -885,7 +885,11 @@ static int __init init_sr(void)
 	rc = register_blkdev(SCSI_CDROM_MAJOR, "sr");
 	if (rc)
 		return rc;
-	return scsi_register_driver(&sr_template.gendrv);
+	rc = scsi_register_driver(&sr_template.gendrv);
+	if (rc)
+		unregister_blkdev(SCSI_CDROM_MAJOR, "sr");
+
+	return rc;
 }
 
 static void __exit exit_sr(void)