usb: dwc2: add multiple clock handling

usb: dwc2: add multiple clock handling

Originally, dwc2 just handle one clock named otg, however, it may have
two or more clock need to manage for some new SoCs, so this adds
change clk to clk's array of dwc2_hsotg to handle more clocks operation.

Change-Id: I661297ef908d9eace2215205018fa94d12cea128
Signed-off-by: Frank Wang <frank.wang@rock-chips.com>