gluon-setup-mode: get status-led from device-tree

With this commit, the status-led is set to be the "led-running"
device-tree alias for targets which do not implement the get_status_led
method in /etc/diag.sh.

package/gluon-setup-mode/files/lib/gluon/setup-mode/rc.d/S96led

@@ -6,6 +6,12 @@ start() {
 	/etc/init.d/led start
 
 	. /etc/diag.sh
-	get_status_led
+
+	get_status_led 2> /dev/null
+
+	if [ -z $status_led ]; then
+		status_led="$running"
+	fi
+
 	status_led_set_timer 1000 300
 }