USB: fix bug in usb_unlink_anchored_urbs()

Irqs must not accidentally be reenabled.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>