usb: gadget: thor: Invoke board specific USB cleanup interface

This patch invokes board-specific USB cleanup (board_usb_cleanup)
function in the thor gadget.

Signed-off-by: Inha Song <ideal.song@samsung.com>

common/cmd_thordown.c

@@ -56,6 +56,7 @@ int do_thor_down(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 
 exit:
 	g_dnl_unregister();
+	board_usb_cleanup(controller_index, USB_INIT_DEVICE);
 done:
 	dfu_free_entities();