usb: xhci: fix spinlock recursion for USB2 test mode

Both xhci_hub_control and xhci_disable_slot tries to hold spinlock, the
spinlock recursion occurs when enters USB2 test mode. Fix it by unlock
spinlock before calling xhci_disable_slot.

Cc: <stable@vger.kernel.org>
Fixes: 0f1d832 ("usb: xhci: Add port test modes support for usb2")
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci-hub.c

@@ -610,12 +610,14 @@ static int xhci_enter_test_mode(struct xhci_hcd *xhci,
 
 	/* Disable all Device Slots */
 	xhci_dbg(xhci, "Disable all slots\n");
+	spin_unlock_irqrestore(&xhci->lock, *flags);
 	for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
 		retval = xhci_disable_slot(xhci, NULL, i);
 		if (retval)
 			xhci_err(xhci, "Failed to disable slot %d, %d. Enter test mode anyway\n",
 				 i, retval);
 	}
+	spin_lock_irqsave(&xhci->lock, *flags);
 	/* Put all ports to the Disable state by clear PP */
 	xhci_dbg(xhci, "Disable all port (PP = 0)\n");
 	/* Power off USB3 ports*/