usb: dwc3: gadget: fix skip LINK_TRB on ISOC

commit 915e202a upstream.

When we reach to link trb, we just need to increase free_slot and then
calculate TRB. Return is not correct, as it will cause wrong TRB DMA
address to fetch in case of update transfer.
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/gadget.c

@@ -754,21 +754,18 @@ static void dwc3_prepare_one_trb(struct dwc3_ep *dep,
 	struct dwc3		*dwc = dep->dwc;
 	struct dwc3_trb		*trb;
 
-	unsigned int		cur_slot;
-
 	dev_vdbg(dwc->dev, "%s: req %p dma %08llx length %d%s%s\n",
 			dep->name, req, (unsigned long long) dma,
 			length, last ? " last" : "",
 			chain ? " chain" : "");
 
-	trb = &dep->trb_pool[dep->free_slot & DWC3_TRB_MASK];
-	cur_slot = dep->free_slot;
-	dep->free_slot++;
-
 	/* Skip the LINK-TRB on ISOC */
-	if (((cur_slot & DWC3_TRB_MASK) == DWC3_TRB_NUM - 1) &&
+	if (((dep->free_slot & DWC3_TRB_MASK) == DWC3_TRB_NUM - 1) &&
 			usb_endpoint_xfer_isoc(dep->endpoint.desc))
-		return;
+		dep->free_slot++;
+
+	trb = &dep->trb_pool[dep->free_slot & DWC3_TRB_MASK];
+	dep->free_slot++;
 
 	if (!req->trb) {
 		dwc3_gadget_move_request_queued(req);