nvme-pci: Suspend queues after deleting them

The driver had been abusing the cq_vector state to know if new submissions
were safe, but that was before we could quiesce blk-mq. If the controller
happens to get an interrupt through while we're suspending those queues,
'no irq handler' warnings may occur.

This patch will disable the interrupts only after the queues are deleted.

Reported-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Tested-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>