arm64: dts: rockchip: rk1808-compute: fix usb3 to peripheral mode

Since compute stick always use as device, and do not need detect
vbus, so fix usb3 dr_mode to peripheral, and set vbus as always on

Change-Id: I886563fd611439110544104ecef42cfb0c386b4c
Signed-off-by: Lin Huang <hl@rock-chips.com>

arch/arm64/boot/dts/rockchip/rk1808-compute.dtsi

@@ -166,6 +166,7 @@
 };
 
 &u2phy_otg {
+	rockchip,vbus-always-on;
 	status = "okay";
 };
 
@@ -179,10 +180,10 @@
 
 &usbdrd3 {
 	status = "okay";
-	extcon = <&u2phy>;
 };
 
 &usbdrd_dwc3 {
+	dr_mode = "peripheral";
 	status = "okay";
 };