added gateway dts in recipe

Author: maidnl

meta-arduino-bsp/recipes-bsp/device-tree/arduino-device-tree.inc

@@ -81,6 +81,7 @@ DTB_OVERLAYS:append:portenta-x9 = " \
 # Portenta-X9 root devicetree
 SRC_URI:append:portenta-x9 = " \
     file://portenta-x9/arduino_portenta-x9.dts \
+    file://portenta-x9/arduino_portenta-x9-gateway.dts \
     file://portenta-x9/arduino_portenta-x9-rpi-cm4-io-board-dsi-panel.dts \
     file://portenta-x9/arduino_portenta-x9-rpi-cm4-io-board-dsi-panel-csi-camera-imx708.dts \
     file://portenta-x9/arduino_portenta-x9-rpi-cm4-io-board-dsi-panel-csi-camera-ov5647.dts \