null_blk: fix memory leak on cleanup
null_blk: fix memory leak on cleanup

Driver was not freeing the memory allocated for internal nullb queues.
This patch frees the memory during driver unload.

Signed-off-by: Matias Bjørling <77666125932addc6fc525b281b518fd8fd2203d8@lightnvm.io>
Signed-off-by: Jens Axboe <cd8c6775e60d6f67a6984377324e5290df3d5358@fb.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs