rockchip: firefly-rk3399: enable CONFIG_USB_DWC3

To fix below build error:
drivers/usb/host/built-in.o: In function `xhci_dwc3_remove':
drivers/usb/host/xhci-dwc3.c:174: undefined reference to `dwc3_shutdown_phy'
drivers/usb/host/built-in.o: In function `xhci_dwc3_probe':
drivers/usb/host/xhci-dwc3.c:130: undefined reference to `dwc3_setup_phy'

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
1 file changed