nvme: use blk_mq_alloc_disk

mainline inclusion
from mainline-v5.15-rc1
commit 5f432cce
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I81XCK

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5f432cceb3e9de5223fa50d882c4a43cab39a3ee



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Switch to use the blk_mq_alloc_disk helper for allocating the
request_queue and gendisk.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Link: https://lore.kernel.org/r/20210816131910.615153-2-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>
conflict:
 drivers/nvme/host/core.c
Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
Signed-off-by: Li Nan <linan122@huawei.com>