block: remove devnode callback from struct block_device_operations

With the removal of the pktcdvd driver, there are no in-kernel users of
the devnode callback in struct block_device_operations, so it can be
safely removed.  If it is needed for new block drivers in the future, it
can be brought back.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20221203140747.1942969-1-gregkh@linuxfoundation.org


Signed-off-by: Jens Axboe <axboe@kernel.dk>