block: remove blk_mq_init_bitmaps

The little work done in blk_mq_init_bitmaps is easier done in the only
caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20250106083531.799976-3-hch@lst.de


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