usb: dwc2: platform: add generic PHY framework support

Get PHY parameters from devicetree and power off usb PHY during
system suspend.

Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Yunzhi Li <lyz@rock-chips.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>