ARM: dts: rockchip: enable usbotg for Popemtal-rk3288 board

Enable USB OTG port on RK3288 Popmetal board, So we can run
some usb gadget functions like Android adb on this board.
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm/boot/dts/rk3288-popmetal.dts

@@ -525,3 +525,7 @@ &uart4 {
 &usbphy {
 	status = "okay";
 };
+
+&usb_otg {
+	status = "okay";
+};