usb: musb: omap2430: fix compile warning

fix the following compile warning:

drivers/usb/musb/omap2430.c: In function 'musb_otg_notifier_work':
drivers/usb/musb/omap2430.c:279:3: warning: 'return' with a value, in
	function returning void
drivers/usb/musb/omap2430.c:282:2: warning: 'return' with a value, in
	function returning void
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/musb/omap2430.c

@@ -283,10 +283,7 @@ static void musb_otg_notifier_work(struct work_struct *data_notifier_work)
 		break;
 	default:
 		dev_dbg(musb->controller, "ID float\n");
-		return NOTIFY_DONE;
 	}
-
-	return NOTIFY_OK;
 }
 
 static int omap2430_musb_init(struct musb *musb)