usb: gadget: renesas_usbhs: support otg pin control

some renesas_usbhs device is supporting OTG external device interface.
In that device, it is necessary to control PWEN/EXTLP on DVSTCTR.
This patch support it.
But renesas_usbhs driver doesn't have OTG support for now.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>