Merge miscellaneous libnvdimm updates for 4.21

* Use common helpers, bitmap_zalloc() and kstrndup(), to replace open
  coded versions.
* Clarify the comments around hotplug vs initial init case for the nfit
  driver.
* Cleanup the libnvdimm init path.

drivers/nvdimm/bus.c

@@ -350,12 +350,12 @@ struct nvdimm_bus *nvdimm_bus_register(struct device *parent,
 	INIT_LIST_HEAD(&nvdimm_bus->mapping_list);
 	init_waitqueue_head(&nvdimm_bus->probe_wait);
 	nvdimm_bus->id = ida_simple_get(&nd_ida, 0, 0, GFP_KERNEL);
-	mutex_init(&nvdimm_bus->reconfig_mutex);
-	badrange_init(&nvdimm_bus->badrange);
 	if (nvdimm_bus->id < 0) {
 		kfree(nvdimm_bus);
 		return NULL;
 	}
+	mutex_init(&nvdimm_bus->reconfig_mutex);
+	badrange_init(&nvdimm_bus->badrange);
 	nvdimm_bus->nd_desc = nd_desc;
 	nvdimm_bus->dev.parent = parent;
 	nvdimm_bus->dev.release = nvdimm_bus_release;