thermal: of: Enable thermal_zoneX when sensor is correctly added

Up till now the thermal_zone mode was by default "disabled". With this
patch the default behavior was changed to "enable".

One can read the mode at:
/sys/class/thermal/thermal_zone0/mode

Tested-by: Javi Merino <[e-mail]>
Reported-by: Abhilash Kesavan <[e-mail]>
Signed-off-by: Lukasz Majewski <[e-mail]>
Signed-off-by: Eduardo Valentin <[e-mail]>

drivers/thermal/of-thermal.c

···
 		if (sensor_specs.np == sensor_np && id == sensor_id) {
 			tzd = thermal_zone_of_add_sensor(child, sensor_np,
 							 data, ops);
+			if (!IS_ERR(tzd))
+				tzd->ops->set_mode(tzd, THERMAL_DEVICE_ENABLED);
+
 			of_node_put(sensor_specs.np);
 			of_node_put(child);
 			goto exit;