usb: core: remove flags variable in __usb_hcd_giveback_urb()

In commit ed194d13 ("usb: core: remove local_irq_save() around
->complete() handler") I removed the only user of the flags variable and
forgot to remove the variable, leading to warning because it is unused
now.
Remove the unused variable.

Fixes: ed194d13 ("usb: core: remove local_irq_save() around ->complete() handler")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -1738,7 +1738,6 @@ static void __usb_hcd_giveback_urb(struct urb *urb)
 	struct usb_hcd *hcd = bus_to_hcd(urb->dev->bus);
 	struct usb_anchor *anchor = urb->anchor;
 	int status = urb->unlinked;
-	unsigned long flags;
 
 	urb->hcpriv = NULL;
 	if (unlikely((urb->transfer_flags & URB_SHORT_NOT_OK) &&