1. free memory during pci_xhci_dev_destroy.
2. add libusb_free_device_list to free the list of devices previously
discovered using libusb_get_device_list().
3. fix possible memory corruption.
Tracked-On: #2892
Signed-off-by: Conghui Chen <conghui.chen@intel.com>
Reviewed-by: Xiaoguang Wu <xiaoguang.wu@intel.com>
Acked-by: Yu Wang <yu1.wang@intel.com>