[SX128x] Added TRNG support

src/modules/SX128x/SX128x.cpp

@@ -1122,6 +1122,12 @@ void SX128x::setRfSwitchPins(RADIOLIB_PIN_TYPE rxEn, RADIOLIB_PIN_TYPE txEn) {
   _mod->setRfSwitchPins(rxEn, txEn);
 }
 
+uint8_t SX128x::random() {
+  // it's unclear whether SX128x can measure RSSI while not receiving a packet
+  // this method is implemented only for PhysicalLayer compatibility
+  return(0);
+}
+
 uint8_t SX128x::getStatus() {
   uint8_t data = 0;
   SPIreadCommand(SX128X_CMD_GET_STATUS, &data, 1);

src/modules/SX128x/SX128x.h

@@ -753,6 +753,13 @@ class SX128x: public PhysicalLayer {
     */
     void setRfSwitchPins(RADIOLIB_PIN_TYPE rxEn, RADIOLIB_PIN_TYPE txEn);
 
+    /*!
+     \brief Dummy random method, to ensure PhysicalLayer compatibility.
+
+     \returns Always returns 0.
+   */
+    uint8_t random();
+
 #ifndef RADIOLIB_GODMODE
   protected:
 #endif