fix: Quick fix to let CRSF be used with MPM wireless trainer - limiations apply (#1724)

* Let's do some dirty hack with MPM RX

Resolves #1671

* Use the right function to sync and shutdown sync on external MPM as well

radio/src/telemetry/multi.h

@@ -108,6 +108,7 @@ struct MultiModuleStatus {
   uint8_t flags;
   uint8_t requiresFailsafeCheck;
   uint8_t failsafeChecked;
+  uint8_t isRXProto;
   tmr10ms_t lastUpdate;
 
   uint8_t protocolPrev = 0;