[mac] remove duplicated method for getting the MAC frame length (#9254)

src/core/mac/mac_frame.cpp

@@ -1214,7 +1214,7 @@ void TxFrame::CopyFrom(const TxFrame &aFromFrame)
         // different FCS size. We adjust the PSDU length after the
         // copy to account for this.
 
-        SetLength(aFromFrame.GetPsduLength() - aFromFrame.GetFcsSize() + GetFcsSize());
+        SetLength(aFromFrame.GetLength() - aFromFrame.GetFcsSize() + GetFcsSize());
     }
 #endif
 }

src/core/mac/mac_frame.hpp

@@ -784,7 +784,7 @@ public:
     bool IsDataRequestCommand(void) const;
 
     /**
-     * Returns the MAC Frame Length.
+     * Returns the MAC Frame Length, namely the IEEE 802.15.4 PSDU length.
      *
      * @returns The MAC Frame Length.
      *
@@ -845,14 +845,6 @@ public:
      */
     uint8_t GetChannel(void) const { return mChannel; }
 
-    /**
-     * Returns the IEEE 802.15.4 PSDU length.
-     *
-     * @returns The IEEE 802.15.4 PSDU length.
-     *
-     */
-    uint16_t GetPsduLength(void) const { return mLength; }
-
     /**
      * Returns a pointer to the PSDU.
      *

src/core/radio/radio_callbacks.cpp

@@ -51,7 +51,7 @@ void Radio::Callbacks::HandleTransmitStarted(Mac::TxFrame &aFrame) { Get<Mac::Su
 void Radio::Callbacks::HandleTransmitDone(Mac::TxFrame &aFrame, Mac::RxFrame *aAckFrame, Error aError)
 {
 #if OPENTHREAD_CONFIG_RADIO_STATS_ENABLE && (OPENTHREAD_FTD || OPENTHREAD_MTD)
-    Get<RadioStatistics>().RecordTxDone(aError, aFrame.GetPsduLength());
+    Get<RadioStatistics>().RecordTxDone(aError, aFrame.GetLength());
 #endif
     Get<Mac::SubMac>().HandleTransmitDone(aFrame, aAckFrame, aError);
 }