While the NVMe specification allows the device to access the host memory
buffer in host DRAM from all power states, hosts will fail access to
DRAM during S3 and similar power states.

Fixes: d916b1be ("nvme-pci: use host managed power state for suspend")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>