usb: musb: gadget: use platform callback to enable vbus

On some platform configurations (like OMAP3+twl4030) it's the platform
code that enables VBUS, not OTG transceiver, so call vbus platform
callback instead, it will then call the transceiver if needed.

This fixes a use case where USB cable is plugged first and gadget
driver is loaded later after that.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_gadget.c

@@ -1848,9 +1848,8 @@ static int musb_gadget_start(struct usb_gadget *g,
 		goto err;
 	}
 
-	if ((musb->xceiv->last_event == USB_EVENT_ID)
-				&& otg->set_vbus)
-		otg_set_vbus(otg, 1);
+	if (musb->xceiv->last_event == USB_EVENT_ID)
+		musb_platform_set_vbus(musb, 1);
 
 	hcd->self.uses_pio_for_control = 1;