arm/dt: hammerhead: Set the usb max speed to high

Hammerhead supports the high speed for USB maximum speed.

Change-Id: Ifd92a5880672ab845d5ec91d6fdb963f80e66d2d
Signed-off-by: Devin Kim <dojip.kim@lge.com>

arch/arm/boot/dts/msm8974-hammerhead/msm8974-hammerhead-usb.dtsi

@@ -21,5 +21,6 @@
 
 	dwc3@f9200000 {
 		no-set-vbus-power;
+		maximum-speed="high";
 	};
 };