nvme-core: check ctrl css before setting up zns

Ensure multiple Command Sets are supported before starting to setup a
ZNS namespace.
Signed-off-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
[hch: move the check around a bit]
Signed-off-by: NChristoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -4096,6 +4096,12 @@ static void nvme_validate_or_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 				nsid);
 			break;
 		}
+		if (!nvme_multi_css(ctrl)) {
+			dev_warn(ctrl->device,
+				"command set not reported for nsid: %d\n",
+				ns->head->ns_id);
+			break;
+		}
 		nvme_alloc_ns(ctrl, nsid, &ids);
 		break;
 	default: