block: cleanup flag_{show,store}

Remove a superfluous argument that flag_show and flag_store currently
take.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240617044918.374608-1-joshi.k@samsung.com


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