usb: dwc2: add support of hi6220

Support hisilicon,hi6220-usb for HiKey board

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>