arm: dts: imx6qdl-gw*: add dr_mode prop to dt to avoid error

The fsl-usb dt bindings in Linux default dr_mode to 'host' for
backward compatibility however U-Boot prints an error if
this property does not exist. Declare it in the Gateworks
Ventana device-trees to avoid the error.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/arch/arm/dts/imx6qdl-gw553x.dtsi b/arch/arm/dts/imx6qdl-gw553x.dtsi
index c15b9cc..b6965f2 100644
--- a/arch/arm/dts/imx6qdl-gw553x.dtsi
+++ b/arch/arm/dts/imx6qdl-gw553x.dtsi
@@ -509,6 +509,7 @@
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_usbotg>;
 	disable-over-current;
+	dr_mode = "otg";
 	status = "okay";
 };