[factory-diags] fix usage of OPENTHREAD_RADIO (#9736)

src/core/diags/factory_diags.cpp

@@ -846,7 +846,7 @@ Error Diags::ProcessCmd(uint8_t aArgsLength, char *aArgs[], char *aOutput, size_
 
     // This `rcp` command is for debugging and testing only, building only when NDEBUG is not defined
     // so that it will be excluded from release build.
-#if !defined(NDEBUG) && defined(OPENTHREAD_RADIO)
+#if OPENTHREAD_RADIO && !defined(NDEBUG)
     if (aArgsLength > 0 && !strcmp(aArgs[0], "rcp"))
     {
         aArgs++;