nvme: Namepace identification descriptor list is optional

Despite NVM Express specification 1.3 requires a controller claiming to
be 1.3 or higher implement Identify CNS 03h (Namespace Identification
Descriptor list), the driver doesn't really need this identification in
order to use a namespace. The code had already documented in comments
that we're not to consider an error to this command.

Return success if the controller provided any response to an
namespace identification descriptors command.

Fixes: 538af88ea7d9de24 ("nvme: make nvme_report_ns_ids propagate error back")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=205679
Reported-by: Ingo Brunberg <ingo_brunberg@web.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: stable@vger.kernel.org # 5.4+
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/core.c

@@ -1735,6 +1735,8 @@ static int nvme_report_ns_ids(struct nvme_ctrl *ctrl, unsigned int nsid,
 		if (ret)
 			dev_warn(ctrl->device,
 				 "Identify Descriptors failed (%d)\n", ret);
+		if (ret > 0)
+			ret = 0;
 	}
 	return ret;
 }