nvme: introduce nvme_sync_io_queues

Introduce sync io queues for some scenarios which just only need sync
io queues not sync all queues.

Signed-off-by: Chao Leng <lengchao@huawei.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>