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.cpp

@@ -244,6 +244,16 @@ static void processMultiStatusPacket(const uint8_t * data, uint8_t module, uint8
   if (wasBinding && !status.isBinding() && getMultiBindStatus(module) == MULTI_BIND_INITIATED)
     setMultiBindStatus(module, MULTI_BIND_FINISHED);
 
+  // Dirty RX protocol detection
+  size_t proto_len = strnlen(status.protocolName, 8);
+  if (proto_len >= 2 &&
+      status.protocolName[proto_len - 2] == 'R' &&
+      status.protocolName[proto_len - 1] == 'X') {
+    status.isRXProto = true;
+  } else {
+    status.isRXProto = false;
+  }
+
   // update timestamp last to avoid race conditions
   status.lastUpdate = get_tmr10ms();
 }

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;

radio/src/telemetry/telemetry.h

@@ -318,7 +318,7 @@ struct ModuleSyncStatus
   tmr10ms_t lastUpdate;  // in 10ms
   int16_t   currentLag;  // in us
   
-  inline bool isValid() {
+  inline bool isValid() const {
     // 2 seconds
     return (get_tmr10ms() - lastUpdate < 200);
   }