libnvdimm/label: Return -ENXIO for no slot in __blk_label_update

Forget to set error code when nd_label_alloc_slot failed, and we
add it to avoid overwritten error code.

Fixes: 0ba1c634 ("libnvdimm: write blk label set")
Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
Link: https://lore.kernel.org/r/20201205115056.2076523-1-zhangqilong3@huawei.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/label.c

@@ -1008,8 +1008,10 @@ static int __blk_label_update(struct nd_region *nd_region,
 		if (is_old_resource(res, old_res_list, old_num_resources))
 			continue; /* carry-over */
 		slot = nd_label_alloc_slot(ndd);
-		if (slot == UINT_MAX)
+		if (slot == UINT_MAX) {
+			rc = -ENXIO;
 			goto abort;
+		}
 		dev_dbg(ndd->dev, "allocated: %d\n", slot);
 
 		nd_label = to_label(ndd, slot);