usb: renesas: gadget: don't assign gadget.dev.release directly

udc-core provides a better way to handle release
methods, let's use it.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/renesas_usbhs/mod_gadget.c

@@ -923,11 +923,6 @@ static int usbhsg_stop(struct usbhs_priv *priv)
 	return usbhsg_try_stop(priv, USBHSG_STATUS_STARTED);
 }
 
-static void usbhs_mod_gadget_release(struct device *pdev)
-{
-	/* do nothing */
-}
-
 int usbhs_mod_gadget_probe(struct usbhs_priv *priv)
 {
 	struct usbhsg_gpriv *gpriv;
@@ -975,7 +970,6 @@ int usbhs_mod_gadget_probe(struct usbhs_priv *priv)
 	 * init gadget
 	 */
 	gpriv->gadget.dev.parent	= dev;
-	gpriv->gadget.dev.release	= usbhs_mod_gadget_release;
 	gpriv->gadget.name		= "renesas_usbhs_udc";
 	gpriv->gadget.ops		= &usbhsg_gadget_ops;
 	gpriv->gadget.max_speed		= USB_SPEED_HIGH;