Drop the idea of supporting multiple firmware

We are not going to support other firmware than KeyboardioFirmware - if need be,
KeyboardioFirmware will be ported to other hardware instead. As such, remove the
traces of code that suggest otherwise.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/Akela-Core.h

@@ -19,15 +19,10 @@
 #pragma once
 
 #ifdef ARDUINO_AVR_MODEL01
-#  define AKELA_KEYBOARDIO
 #  define AKELA_KEYBOARDIO_MODEL01
 #endif
 
-#ifdef AKELA_KEYBOARDIO
-#  include <KeyboardioFirmware.h>
-#else
-#  error Target firmware integration is not supported
-#endif
+#include <KeyboardioFirmware.h>
 
 #define DEFAULT_TIMEOUT 40