hwmon: Register thermal zone only if 'dev' parameter was provided

Rgistering a thermal zone uses devm_kzalloc(), which requires
a pointer to the parent device.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -608,7 +608,7 @@ __hwmon_device_register(struct device *dev, const char *name, void *drvdata,
 	if (err)
 		goto free_hwmon;
 
-	if (chip && chip->ops->read &&
+	if (dev && chip && chip->ops->read &&
 	    chip->info[0]->type == hwmon_chip &&
 	    (chip->info[0]->config[0] & HWMON_C_REGISTER_TZ)) {
 		const struct hwmon_channel_info **info = chip->info;