usb: dwc3: gadget: return 0 if we try to Wakeup in superspeed

Instead of returning -EINVAL when someone calls
__dwc3_gadget_wakeup() in speeds > highspeed, let's
return 0. There are no problems for the driver for
calling it in superspeed as we cleanly just return.

This avoids an annoying WARN_ONCE() always
triggering during superspeed enumeration with LPM
enabled.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/gadget.c

@@ -1431,7 +1431,7 @@ static int __dwc3_gadget_wakeup(struct dwc3 *dwc)
 	if ((speed == DWC3_DSTS_SUPERSPEED) ||
 	    (speed == DWC3_DSTS_SUPERSPEED_PLUS)) {
 		dwc3_trace(trace_dwc3_gadget, "no wakeup on SuperSpeed\n");
-		return -EINVAL;
+		return 0;
 	}
 
 	link_state = DWC3_DSTS_USBLNKST(reg);