usb: dwc3: dwc3-of-simple: Add support for dwc3 of Hisilicon Soc Platform

This patch adds support for the poweron and shutdown of dwc3 core
on Hisilicon Soc Platform.

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Yu Chen <chenyu56@huawei.com>