nvme/pci: Log PCI_STATUS when the controller dies

nvme/pci: Log PCI_STATUS when the controller dies

When debugging nvme controller crashes, it's nice to know whether
the controller died cleanly so that the failure is just reflected in
CSTS, it died and put an error in PCI_STATUS, or whether it died so
badly that it stopped responding to PCI configuration space reads.

I've seen a failure that gives 0xffff in PCI_STATUS on a Samsung
"SM951 NVMe SAMSUNG 256GB" with firmware "BXW75D0Q".

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Fixed up white space and hunk reject.

Signed-off-by: Jens Axboe <axboe@fb.com>