pktcdvd: simplify the class_pktcdvd logic

There is no need to dynamically create and destroy the class_pktcdvd
structure, just make it static and remove the memory allocation logic
which simplifies and cleans up the logic a lot.

Cc: linux-block@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20230331164724.319703-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>