block: avoid quiesce while elevator init

hulk inclusion
category: bugfix
bugzilla: 185781 https://gitee.com/openeuler/kernel/issues/I4DDEL



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As blk_mq_quiesce_queue in elevator_init_mq will wait a RCU gap which want to
make sure no IO will happen while blk_mq_init_sched. If there is lots of
device will lead to boot slowly.
To address this issue, according to Lei Ming's suggestion:
"We are called before adding disk, when there isn't any FS I/O, so freezing
queue plus canceling dispatch work is enough to drain any dispatch activities
originated from passthrough requests, then no need to quiesce queue which may
add long boot latency, especially when lots of disks are involved."

Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>