usb: host: xhci: remove unused trb var in xhci_irq()

The union xhci_trb *trb variable is defined and assigned
inside the xHCI IRQ handler function but is never used.
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-ring.c

@@ -2706,13 +2706,11 @@ irqreturn_t xhci_irq(struct usb_hcd *hcd)
 {
 	struct xhci_hcd *xhci = hcd_to_xhci(hcd);
 	u32 status;
-	union xhci_trb *trb;
 	u64 temp_64;
 	union xhci_trb *event_ring_deq;
 	dma_addr_t deq;
 
 	spin_lock(&xhci->lock);
-	trb = xhci->event_ring->dequeue;
 	/* Check if the xHC generated the interrupt, or the irq is shared */
 	status = xhci_readl(xhci, &xhci->op_regs->status);
 	if (status == 0xffffffff)