blk: Don't forget call io_uring_unregister_files.

blk: Don't forget call io_uring_unregister_files.

When using vstart.sh to deploy ceph cluster w/ bdev_ioring=true, met the
following error messages:
> /root/ceph/build/bin/ceph-osd -i 0 -c /root/ceph/build/ceph.conf --mkfs --key AQByU/JmoSTAExAApXM0Q6Et9xgfMJ3MJg7wSw== --osd-uuid e135fff2-a02c-415a-b1fe-c154a4e61c13
>2024-09-24T13:51:46.770+0800 7c71966245c0 -1 bdev(0x5c937f62f000 /root/ceph/build/dev/osd0/block) open open w/ O_EXCL
> 2024-09-24T13:51:46.772+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) _read_bdev_label unable to decode label /root/ceph/build/dev/osd0/block at offset 102: void bluestore_bdev_label_t::decode(ceph::buffer::v15_2_0::list::const_iterator&) decode past end of struct encoding: Malformed input [buffer:3]
> 2024-09-24T13:51:46.772+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) _read_multi_bdev_label label at 0x40000000 correct, but osd_uuid=b89e2e1d-dc77-45fb-9a0b-34eb0a35c9a4 need=e135fff2-a02c-415a-b1fe-c154a4e61c13
> 2024-09-24T13:51:46.772+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) _read_multi_bdev_label label at 0x280000000 correct, but osd_uuid=b89e2e1d-dc77-45fb-9a0b-34eb0a35c9a4 need=e135fff2-a02c-415a-b1fe-c154a4e61c13
> 2024-09-24T13:51:46.772+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) _read_multi_bdev_label label at 0x1900000000 correct, but osd_uuid=b89e2e1d-dc77-45fb-9a0b-34eb0a35c9a4 need=e135fff2-a02c-415a-b1fe-c154a4e61c13
> 2024-09-24T13:51:46.773+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) _read_multi_bdev_label label at 0xfa00000000 correct, but osd_uuid=b89e2e1d-dc77-45fb-9a0b-34eb0a35c9a4 need=e135fff2-a02c-415a-b1fe-c154a4e61c13
> 2024-09-24T13:51:46.773+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0/block) No valid bdev label found
> 2024-09-24T13:51:47.022+0800 7c71966245c0 -1 bluestore(/root/ceph/build/dev/osd0) _read_fsid unparsable uuid
> 2024-09-24T13:51:47.022+0800 7c71966245c0 -1 bdev(0x5c937f62f000 /root/ceph/build/dev/osd0/block) open open w/ O_EXCL
> 2024-09-24T13:51:47.022+0800 7c71966245c0 -1 bdev(0x5c937f62f000 /root/ceph/build/dev/osd0/block) open open got: (16) Device or resource busy0

This because we use io_uring_register_files when use ioruing. But we
forget to unreister those files.

Signed-off-by: Ma, Jianpeng <jianpeng.ma@intel.com>