nvme: disable irqs in nvme_freeze_queues

The queue_lock needs to be taken with irqs disabled.  This is mostly
due to the old pre blk-mq usage pattern, but we've also picked it up
in most of the few places where we use the queue_lock with blk-mq.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>