Multiprotocol working on sky9x and co (#4409)

* MULTI working on sky9x

* Fix crash with module OFF

* Cosmetics

* Compilation fix / cosmetics

* Typo....

* Multi now available on all ARM platforms

* Does this help?

* Compilation fix

radio/src/opentx.cpp

@@ -2492,7 +2492,7 @@ void opentxInit(OPENTX_INIT_ARGS)
 #endif  // #if !defined(EEPROM)
 
 #if defined(SERIAL2)
-  serial2Init(g_eeGeneral.serial2Mode, MODEL_TELEMETRY_PROTOCOL());
+  serial2Init(g_eeGeneral.serial2Mode, modelTelemetryProtocol());
 #endif
 
 #if defined(PCBTARANIS)