block/sed-opal: Introduce free_opal_dev to free the structure and clean up state

Before we free the opal structure we need to clean up any saved
locking ranges that the user had told us to unlock from a suspend.

Signed-off-by: Scott Bauer <scott.bauer@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>