configs: rockchip: rock960: enable USB3 support

Enable USB3 support via the dwc3 XHCI driver.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
diff --git a/configs/rock960-rk3399_defconfig b/configs/rock960-rk3399_defconfig
index 90115e9..5be3638 100644
--- a/configs/rock960-rk3399_defconfig
+++ b/configs/rock960-rk3399_defconfig
@@ -55,5 +55,8 @@
 CONFIG_USB_ETHER_MCS7830=y
 CONFIG_USB_ETHER_RTL8152=y
 CONFIG_USB_ETHER_SMSC95XX=y
+CONFIG_USB_XHCI_HCD=y
+CONFIG_USB_XHCI_DWC3=y
+# CONFIG_USB_XHCI_ROCKCHIP is not set
 CONFIG_USE_TINY_PRINTF=y
 CONFIG_ERRNO_STR=y