usb: dwc3: gadget: Store resource index of start cmd

As long as the START_TRANSFER command completes, it provides the
resource index of the endpoint. Use this when we need to issue
END_TRANSFER command to an isoc endpoint to retry with a new
XferNotReady event.
Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc3/gadget.c

@@ -387,8 +387,11 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned cmd,
 
 	trace_dwc3_gadget_ep_cmd(dep, cmd, params, cmd_status);
 
-	if (ret == 0 && DWC3_DEPCMD_CMD(cmd) == DWC3_DEPCMD_STARTTRANSFER) {
+	if (DWC3_DEPCMD_CMD(cmd) == DWC3_DEPCMD_STARTTRANSFER) {
+		if (ret == 0)
 			dep->flags |= DWC3_EP_TRANSFER_STARTED;
+
+		if (ret != -ETIMEDOUT)
 			dwc3_gadget_ep_get_transfer_index(dep);
 	}