scsi: sr: Fix sr_probe() missing mutex_destroy

If the device minor cannot be allocated or the cdrom fails to be registered
then the mutex should be destroyed.

Link: https://lore.kernel.org/r/06e9de38-eeed-1cab-5e08-e889288935b3@0882a8b5-c6c3-11e9-b005-00805fc181fe
Fixes: 51a858817d ("scsi: sr: get rid of sr global mutex")
Signed-off-by: Simon Arlott <simon@octiron.net>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sr.c

@@ -813,6 +813,7 @@ static int sr_probe(struct device *dev)
 
 fail_put:
 	put_disk(disk);
+	mutex_destroy(&cd->lock);
 fail_free:
 	kfree(cd);
 fail: