Change/fix few remaining kThreadError (referenced in comments) to OT_ERROR. (#1822)

include/openthread/openthread.h

@@ -154,11 +154,11 @@ extern "C" {
 OTAPI const char *OTCALL otGetVersionString(void);
 
 /**
- * This function converts a otError enum into a string.
+ * This function converts an otError enum into a string.
  *
- * @param[in]  aError     A otError enum.
+ * @param[in]  aError     An otError enum.
  *
- * @returns  A string representation of a ThreadError.
+ * @returns  A string representation of an otError.
  *
  */
 OTAPI const char *OTCALL otThreadErrorToString(otError aError);

src/ncp/ncp_spi.cpp

@@ -359,7 +359,7 @@ void NcpSpi::HandleRxFrame(void)
         otPlatSpiSlavePrepareTransaction(mEmptySendFrameFullAccept, kSpiHeaderLength, mReceiveFrame,
                                          sizeof(mReceiveFrame), false);
 
-        // No need to check the error status. Getting `kThreadError_Busy`
+        // No need to check the error status. Getting `OT_ERROR_BUSY`
         // is OK as everything will be set up properly from callback when
         // the current transaction is completed.
     }