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/target/arm/tms320dm320/system-dm320.c

@@ -369,9 +369,11 @@ void system_init(void)
 #endif
 
 #ifdef SANSA_CONNECT
+#ifndef HAVE_WIFI
     /* keep WIFI CS and reset high to save power */
     IO_GIO_DIR0 &= ~((1 << 4) /* CS */ | (1 << 3) /* reset */);
     IO_GIO_BITSET0 = (1 << 4) | (1 << 3);
+#endif
 
     i2c_init();
     avr_hid_init();