usb: renesas_usbhs: fixup signal the driver that cable was disconnected

current renesas_usbhs is using new style udc_start/stop from
af1d7056


(usb: gadget: renesas: convert to new style).

cable disconnected signal was needed.
This patch fixup it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>