usb: dwc2: disable power_down on rockchip devices

 The bug would let the usb controller enter partial power down,
 which was formally known as hibernate, upon boot if nothing was plugged
 in to the port. Partial power down couldn't be exited properly, so any
 usb devices plugged in after boot would not be usable.

 Before the name change, params.hibernation was false by default, so
 _dwc2_hcd_suspend() would skip entering hibernation. With the
 rename, _dwc2_hcd_suspend() was changed to use  params.power_down
 to decide whether or not to enter partial power down.

 Since params.power_down is non-zero by default, it needs to be set
 to 0 for rockchip devices to restore functionality.

 This bug was reported in the linux-usb thread:
 REGRESSION: usb: dwc2: USB device not seen after boot

 The commit that caused this regression is:
6d23ee9c

Signed-off-by: SolidHal <hal@halemmerich.com>
Acked-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>