usb: xhci: remove unused variable ep_ring

Fix the build warning about variable 'ep_ring' set but not used

[Minor commit message change -Mathias]
Signed-off-by: NCorentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-ring.c

@@ -1992,7 +1992,6 @@ static int process_ctrl_td(struct xhci_hcd *xhci, struct xhci_td *td,
 	struct xhci_virt_ep *ep, int *status)
 {
 	struct xhci_virt_device *xdev;
-	struct xhci_ring *ep_ring;
 	unsigned int slot_id;
 	int ep_index;
 	struct xhci_ep_ctx *ep_ctx;
@@ -2004,7 +2003,6 @@ static int process_ctrl_td(struct xhci_hcd *xhci, struct xhci_td *td,
 	slot_id = TRB_TO_SLOT_ID(le32_to_cpu(event->flags));
 	xdev = xhci->devs[slot_id];
 	ep_index = TRB_TO_EP_ID(le32_to_cpu(event->flags)) - 1;
-	ep_ring = xhci_dma_to_transfer_ring(ep, le64_to_cpu(event->buffer));
 	ep_ctx = xhci_get_ep_ctx(xhci, xdev->out_ctx, ep_index);
 	trb_comp_code = GET_COMP_CODE(le32_to_cpu(event->transfer_len));
 	requested = td->urb->transfer_buffer_length;