Revert "block/wbt: fix negative inflight counter when remove scsi device"

hulk inclusion
category: bugfix
bugzilla: 187584, https://gitee.com/openeuler/kernel/issues/I5QW2R


CVE: NA

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This reverts commit 37838982.

There are two wbt_enable_default() in bfq_exit_queue(). Although it will
not lead to no fault, revert one.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>