NVMe: fail pci initialization if the device doesn't have any BARs

The PCI init of NVMe doesn't check for valid bars before proceeding
to map and use BAR 0. If the device is hosed (or firmware is), then
we should catch this case and give up early.

This fixes a:

[ 1662.035778] WARNING: CPU: 0 PID: 4 at arch/x86/mm/ioremap.c:63 __ioremap_check_ram+0xa7/0xc0()

and later badness on such a device.
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/block/nvme-core.c

@@ -2156,6 +2156,9 @@ static int nvme_dev_map(struct nvme_dev *dev)
 	dev->entry[0].vector = pdev->irq;
 	pci_set_master(pdev);
 	bars = pci_select_bars(pdev, IORESOURCE_MEM);
+	if (!bars)
+		goto disable_pci;
+
 	if (pci_request_selected_regions(pdev, bars, "nvme"))
 		goto disable_pci;