rock960: Enable USB Gadget

Enable DWC3 core, gadget for rock960 board.

This would help to use fastboot by default.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/configs/rock960-rk3399_defconfig b/configs/rock960-rk3399_defconfig
index 979ca0f..d0ad686 100644
--- a/configs/rock960-rk3399_defconfig
+++ b/configs/rock960-rk3399_defconfig
@@ -57,6 +57,8 @@
 CONFIG_USB_ETHER_MCS7830=y
 CONFIG_USB_ETHER_RTL8152=y
 CONFIG_USB_ETHER_SMSC95XX=y
+CONFIG_USB_GADGET=y
+CONFIG_USB_DWC3=y
 CONFIG_USE_TINY_PRINTF=y
 CONFIG_SPL_TINY_MEMSET=y
 CONFIG_ERRNO_STR=y