rk3399: add a empty "sys_proto.h" header file

driver/usb/dwc3/gadget.c need a "sys_proto.h" header file, add a
empty one to make compile success.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>
1 file changed