tools/testing/nvdimm: fix missing newline in nfit_test_dimm 'handle' attribute

Sysfs userspace tooling generally expects the kernel to emit a newlines
when reading sysfs attributes.

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

tools/testing/nvdimm/test/nfit.c

@@ -1193,7 +1193,7 @@ static ssize_t handle_show(struct device *dev, struct device_attribute *attr,
 	if (dimm < 0)
 		return dimm;
 
-	return sprintf(buf, "%#x", handle[dimm]);
+	return sprintf(buf, "%#x\n", handle[dimm]);
 }
 DEVICE_ATTR_RO(handle);