libnvdimm, test: add mock SMART data payload

Provide simulated SMART data to enable the ndctl implementation of SMART
data retrieval and parsing.

The payload is defined here, "Section 4.1 SMART and Health Info
(Function Index 1)":

    http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/bus.c

@@ -783,6 +783,9 @@ int __init nvdimm_bus_init(void)
 {
 	int rc;
 
+	BUILD_BUG_ON(sizeof(struct nd_smart_payload) != 128);
+	BUILD_BUG_ON(sizeof(struct nd_smart_threshold_payload) != 8);
+
 	rc = bus_register(&nvdimm_bus_type);
 	if (rc)
 		return rc;