Revert "drivers: thermal: parent virtual hwmon with thermal zone"

Commit b82715fdd4 introduces
a 'device' subdirectory under /sys/class/hwmon/hwmonX/ directory,
for the thermal_zone hwmon devices. And this results in different
handling by libsensors.

The problem is reported and discussed in this thread
http://marc.info/?l=linux-pm&m=138229306109596&w=2

This patch reverts commit b82715fdd4.

Reported-by: Arnaud Ebalard <arno@natisbad.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/thermal_hwmon.c

@@ -159,7 +159,7 @@ int thermal_add_hwmon_sysfs(struct thermal_zone_device *tz)
 
 	INIT_LIST_HEAD(&hwmon->tz_list);
 	strlcpy(hwmon->type, tz->type, THERMAL_NAME_LENGTH);
-	hwmon->device = hwmon_device_register(&tz->device);
+	hwmon->device = hwmon_device_register(NULL);
 	if (IS_ERR(hwmon->device)) {
 		result = PTR_ERR(hwmon->device);
 		goto free_mem;