mtd/ubi/block: Fix uaf problem in ubiblock_cleanup

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I81XCK



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put_disk should be placed after idr_remove, otherwise it will trigger
the uaf problem of dev->gd.

Fixes: 77567b25 ("ubi: use blk_mq_alloc_disk and blk_cleanup_disk")
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Signed-off-by: Li Nan <linan122@huawei.com>