dm: switch to rq-based after queue is initialized

hulk inclusion
category: bugfix
bugzilla: 187345, https://gitee.com/openeuler/kernel/issues/I5L5ZG


CVE: NA

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Otherwise, null pointer crash can be triggered to handle bio in
blk_mq_submit_bio() while queue is not initialized.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>