usb: xhci: dbc: remove redundant pointer dbc

Pointer dbc is being assigned but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
variable 'dbc' set but not used [-Wunused-but-set-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-dbgcap.c

@@ -909,11 +909,9 @@ static ssize_t dbc_store(struct device *dev,
 			 struct device_attribute *attr,
 			 const char *buf, size_t count)
 {
-	struct xhci_dbc		*dbc;
 	struct xhci_hcd		*xhci;
 
 	xhci = hcd_to_xhci(dev_get_drvdata(dev));
-	dbc = xhci->dbc;
 
 	if (!strncmp(buf, "enable", 6))
 		xhci_dbc_start(xhci);