xhci: refuse loading if nousb is used

commit 1eaf35e4 upstream.

The module should fail to load.
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: xhci_hcd_init() registers the PCI driver, so
 check before doing that rather than at the end of the function]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/host/xhci.c

@@ -4300,6 +4300,9 @@ static int __init xhci_hcd_init(void)
 {
 	int retval;
 
+	if (usb_disabled())
+		return -ENODEV;
+
 	retval = xhci_register_pci();
 	if (retval < 0) {
 		printk(KERN_DEBUG "Problem registering PCI driver.");