block: Simplify the allocation of slab caches

Use the new KMEM_CACHE() macro instead of direct kmem_cache_create
to simplify the creation of SLAB caches.

Signed-off-by: Kunwu Chan <chentao@kylinos.cn>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20240131094323.146659-1-chentao@kylinos.cn


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