hw/block/nvme: fix legacy namespace registration

Moving namespace registration to the nvme-ns realization function had
the unintended side-effect of breaking legacy namespace registration.
Fix this.

Fixes: 15d024d4aa ("hw/block/nvme: split setup and register for namespace")
Reported-by: Alexander Graf <agraf@csgraf.de>
Cc: Minwoo Im <minwoo.im.dev@gmail.com>
Tested-by: Alexander Graf <agraf@csgraf.de>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>

hw/block/nvme.c

@@ -4507,6 +4507,10 @@ static void nvme_realize(PCIDevice *pci_dev, Error **errp)
         if (nvme_ns_setup(ns, errp)) {
             return;
         }
+
+        if (nvme_register_namespace(n, ns, errp)) {
+            return;
+        }
     }
 }