Fix libusb config descriptor leak

The descriptor received from libusb_get_active_config_descriptor was
never freed. Thus, when opening a channel repeatedly, more and more
memory was leaked (tested with valgrind).

src/ccid_usb.c

@@ -607,6 +607,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  usb_interface = get_ccid_usb_interface(config_desc, &num);
  if (usb_interface == NULL)
  {
+ libusb_free_config_descriptor(config_desc);
  (void)libusb_close(dev_handle);
  if (0 == num)
  DEBUG_CRITICAL3("Can't find a CCID interface on %d/%d",
@@ -618,6 +619,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  device_descriptor = get_ccid_device_descriptor(usb_interface);
  if (NULL == device_descriptor)
  {
+ libusb_free_config_descriptor(config_desc);
  (void)libusb_close(dev_handle);
  DEBUG_CRITICAL3("Unable to find the device descriptor for %d/%d",
  bus_number, device_address);
@@ -628,6 +630,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  interface = usb_interface->altsetting->bInterfaceNumber;
  if (interface_number >= 0 && interface != interface_number)
  {
+ libusb_free_config_descriptor(config_desc);
  /* an interface was specified and it is not the
  * current one */
  DEBUG_INFO3("Found interface %d but expecting %d",
@@ -644,6 +647,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  r = libusb_claim_interface(dev_handle, interface);
  if (r < 0)
  {
+ libusb_free_config_descriptor(config_desc);
  (void)libusb_close(dev_handle);
  DEBUG_CRITICAL4("Can't claim interface %d/%d: %s",
  bus_number, device_address, libusb_error_name(r));
@@ -660,6 +664,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  /* check for firmware bugs */
  if (ccid_check_firmware(&desc))
  {
+ libusb_free_config_descriptor(config_desc);
  (void)libusb_close(dev_handle);
  return_value = STATUS_UNSUCCESSFUL;
  goto end2;
@@ -760,6 +765,7 @@ status_t OpenUSBByName(unsigned int reader_index, /*@null@*/ char *device)
  else
  usbDevice[reader_index].multislot_extension = NULL;
 
+ libusb_free_config_descriptor(config_desc);
  goto end;
  }
  }