libnvdimm: handle locked label storage areas

Per the latest version of the "NVDIMM DSM Interface Example" [1], the
label data retrieval routine can report a "locked" status. In this case
all regions associated with that DIMM are disabled until the label area
is unlocked. Provide generic libnvdimm enabling for NVDIMMs with label
data area locking capabilities.

[1]: http://pmem.io/documents/

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
index 7d1a3db..fac1e9f 100644
--- a/drivers/nvdimm/dimm_devs.c
+++ b/drivers/nvdimm/dimm_devs.c
@@ -67,6 +67,7 @@
 	struct nvdimm_bus *nvdimm_bus = walk_to_nvdimm_bus(ndd->dev);
 	struct nvdimm_bus_descriptor *nd_desc;
 	int rc = validate_dimm(ndd);
+	int cmd_rc = 0;
 
 	if (rc)
 		return rc;
@@ -76,8 +77,11 @@
 
 	memset(cmd, 0, sizeof(*cmd));
 	nd_desc = nvdimm_bus->nd_desc;
-	return nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
-			ND_CMD_GET_CONFIG_SIZE, cmd, sizeof(*cmd), NULL);
+	rc = nd_desc->ndctl(nd_desc, to_nvdimm(ndd->dev),
+			ND_CMD_GET_CONFIG_SIZE, cmd, sizeof(*cmd), &cmd_rc);
+	if (rc < 0)
+		return rc;
+	return cmd_rc;
 }
 
 int nvdimm_init_config_data(struct nvdimm_drvdata *ndd)