witherspoon.dts: Enable the USB vhub (device)

The Aspeed vhub device driver is already enabled in the defconfig, make use of it in the witherspoon platform.

---
 arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts | 4 ++++
 1 file changed, 4 insertions(+)

index b933ced..8ebe35e 100644
@@ -634,6 +634,10 @@
 	memory-region = <&gfx_memory>;
 };
 
+&vhub {
+	status = "okay";
+};
+
 &pinctrl {
 	aspeed,external-nodes = <&gfx &lhc>;
 };

1.8.3.1