xhci: dbc: Change to pass dbc pointer to xhci_do_dbc_stop()

Pass the dbc pointer instead of xhci_hcd pointer in order to
decouple xhci and dbc.

xhci_do_dbc_stop() only used xhci to get the dbc pointer.
Pass the dbc pointer instead as a parameter

No functional changes
This change helps decoupling xhci and DbC
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200723144530.9992-14-mathias.nyman@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-dbgcap.c

@@ -500,10 +500,8 @@ static int xhci_do_dbc_start(struct xhci_hcd *xhci)
 	return 0;
 }
 
-static int xhci_do_dbc_stop(struct xhci_hcd *xhci)
+static int xhci_do_dbc_stop(struct xhci_dbc *dbc)
 {
-	struct xhci_dbc		*dbc = xhci->dbc;
-
 	if (dbc->state == DS_DISABLED)
 		return -1;
 
@@ -550,7 +548,7 @@ static void xhci_dbc_stop(struct xhci_hcd *xhci)
 		xhci_dbc_tty_unregister_device(xhci);
 
 	spin_lock_irqsave(&dbc->lock, flags);
-	ret = xhci_do_dbc_stop(xhci);
+	ret = xhci_do_dbc_stop(dbc);
 	spin_unlock_irqrestore(&dbc->lock, flags);
 
 	if (!ret) {