xhci: dbc: Fix memory leak in xhci_alloc_dbc()

If DbC is already in use, then the allocated memory for the xhci_dbc struct
doesn't get freed before returning NULL, which leads to a memleak.

Fixes: 53467594 ("xhci: dbc: refactor xhci_dbc_init()")
Cc: stable@vger.kernel.org
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20220921123450.671459-3-mathias.nyman@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-dbgcap.c

@@ -988,7 +988,7 @@ xhci_alloc_dbc(struct device *dev, void __iomem *base, const struct dbc_driver *
 	dbc->driver = driver;
 
 	if (readl(&dbc->regs->control) & DBC_CTRL_DBC_ENABLE)
-		return NULL;
+		goto err;
 
 	INIT_DELAYED_WORK(&dbc->event_work, xhci_dbc_handle_events);
 	spin_lock_init(&dbc->lock);