Sansa Connect: Initial libertas WiFi driver port

Import non-free firmware image from linux-firmware package.

Firmware loading works but is disabled at compile time because just
loading firmware without configuring device results in higher power
consumption without any benefit to end user.

Change-Id: I8fd252c49385ede1ea4e0f9b1e29adeb331ab8ae

firmware/export/wifi.h

@@ -0,0 +1,29 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2021 by Tomasz Moń
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#ifndef WIFI_H
+#define WIFI_H
+
+#include "config.h"
+
+void wifi_init(void) INIT_ATTR;
+
+#endif