[diag] fix processing platform command (#4099)

src/core/diags/factory_diags.cpp

@@ -475,15 +475,7 @@ exit:
     {
     case OT_ERROR_NONE:
 
-        if (argCount >= 1)
-        {
-            ProcessCmd(argCount - 1, (argCount == 1) ? NULL : &argVector[1], aOutput, aOutputMaxLen);
-        }
-        else
-        {
-            ProcessCmd(0, NULL, aOutput, aOutputMaxLen);
-        }
-
+        ProcessCmd(argCount, &argVector[0], aOutput, aOutputMaxLen);
         break;
 
     case OT_ERROR_NO_BUFS:

src/ncp/ncp_base.cpp

@@ -1288,6 +1288,16 @@ otError NcpBase::HandlePropertySet_SPINEL_PROP_NEST_STREAM_MFG(uint8_t aHeader)
     VerifyOrExit(error == OT_ERROR_NONE, error = WriteLastStatusFrame(aHeader, ThreadErrorToSpinelStatus(error)));
 
     output[sizeof(output) - 1] = '\0';
+
+#if OPENTHREAD_MTD || OPENTHREAD_FTD
+    // TODO do not pass mfg prefix
+    // skip mfg prefix from wpantund
+    if (memcmp(string, "mfg ", 4) == 0)
+    {
+        string += 4;
+    }
+#endif
+
     otDiagProcessCmdLine(mInstance, string, output, sizeof(output) - 1);
 
     // Prepare the response