usb: isp1760: do not reset retval

We do not really need to reset retval before get used bellow.
This will avoid the clang-analyzer warning:

drivers/usb/isp1760/isp1760-hcd.c:1919:2: warning: Value stored to 'retval' is never read [clang-analyzer-deadcode.DeadStores]
        retval = 0;

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210819180929.1327349-4-rui.silva@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/isp1760/isp1760-hcd.c

@@ -1919,7 +1919,6 @@ static int isp1760_urb_enqueue(struct usb_hcd *hcd, struct urb *urb,
 	if (list_empty(&new_qtds))
 		return -ENOMEM;
 
-	retval = 0;
 	spin_lock_irqsave(&priv->lock, spinflags);
 
 	if (!test_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags)) {