usb: cdns3: gadget: initialize link_trb as NULL

There is an uninitialized variable "link_trb" usage at function cdns3_ep_run_transfer.
Fixed it by initialize "link_trb" as NULL.

Fixes: 4e218882eb ("usb: cdns3: gadget: improve the dump TRB operation at cdns3_ep_run_transfer")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>

drivers/usb/cdns3/gadget.c

@@ -1114,7 +1114,7 @@ static int cdns3_ep_run_transfer(struct cdns3_endpoint *priv_ep,
 	struct cdns3_device *priv_dev = priv_ep->cdns3_dev;
 	struct cdns3_request *priv_req;
 	struct cdns3_trb *trb;
-	struct cdns3_trb *link_trb;
+	struct cdns3_trb *link_trb = NULL;
 	dma_addr_t trb_dma;
 	u32 togle_pcs = 1;
 	int sg_iter = 0;