usb: dwc3: gadget: WARN() in case of unknown IRQ

if an unknown IRQ event is triggered, that means
the HW is really misbehaving. Instead of printing
a debug message, let's WARN() so users report
when that happens.
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/dwc3/gadget.c

@@ -2518,7 +2518,7 @@ static void dwc3_gadget_interrupt(struct dwc3 *dwc,
 		dev_vdbg(dwc->dev, "Overflow\n");
 		break;
 	default:
-		dev_dbg(dwc->dev, "UNKNOWN IRQ %d\n", event->type);
+		dev_WARN(dwc->dev, "UNKNOWN IRQ %d\n", event->type);
 	}
 }