NVMe: Discard errors adding namespaces

Errors encountered while discovering namespaces are not fatal and we should continue adding the device. Erroring out from there before would leave namespaces registered as block devices but the nvme device and queues would have been deleted, which isn't good.

This patch was discussed here:

http://merlin.infradead.org/pipermail/linux-nvme/2013-April/000198.html

In case there are errors or we can't add any namespaces, it would be helpful if we had the character device from here:

http://merlin.infradead.org/pipermail/linux-nvme/2013-February/000138.html

I can resubmit the character device patch to merge with the nvme scsi commits.

---
 drivers/block/nvme-core.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

index a89f7db..5cdfc3a 100644
@@ -1556,6 +1556,7 @@ static int nvme_dev_add(struct nvme_dev *dev)
 	list_for_each_entry(ns, &dev->namespaces, list)
 		add_disk(ns->disk);
 
+	res = 0;
 	goto out;
 
  out_free:

1.7.0.4