usb: dwc2: gadget: Fix issue in dwc2_gadget_start_isoc()

In case of requests queue is empty reset EP target_frame to
initial value.

This allow restarting ISOC traffic in case when function
driver queued requests with interruptions.
Tested-by: Zeng Tao <prime.zeng@hisilicon.com>
Signed-off-by: Minas Harutyunyan <hminas@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc2/gadget.c

@@ -884,6 +884,7 @@ static void dwc2_gadget_start_isoc_ddma(struct dwc2_hsotg_ep *hs_ep)
 	struct dwc2_dma_desc *desc;
 
 	if (list_empty(&hs_ep->queue)) {
+		hs_ep->target_frame = TARGET_FRAME_INITIAL;
 		dev_dbg(hsotg->dev, "%s: No requests in queue\n", __func__);
 		return;
 	}