nvme/pci: move cqe check after device shutdown

commit fa46c6fb

 upstream.

Many users have reported nvme triggered irq_startup() warnings during
shutdown. The driver uses the nvme queue's irq to synchronize scanning
for completions, and enabling an interrupt affined to only offline CPUs
triggers the alarming warning.

Move the final CQE check to after disabling the device and all
registered interrupts have been torn down so that we do not have any
IRQ to synchronize.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206509
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>