ARM: dts: imx51-zii-rdu1: limit usbh1 to full-speed

On RDU1, imx51 usbh1 interface is either not used, or used via external
block that breaks USB2 signalling.

To keep things working if high-speed device gets connected to that
block, use ChipIdea feature to limit port to full speed.
Signed-off-by: NNikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: NLucas Stach <l.stach@pengutronix.de>
Signed-off-by: NShawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx51-zii-rdu1.dts

@@ -589,6 +589,7 @@
 	phy_type = "ulpi";
 	fsl,usbphy = <&usbh1phy>;
 	disable-over-current;
+	maximum-speed = "full-speed";
 	vbus-supply = <&reg_5p0v_main>;
 	status = "okay";
 };