Fix typo in unused member function.

--- 6.18.1/include/plugin.h	2022-02-02 11:43:31.000000000 +0000
+++ 6.18.1/include/plugin.h	2025-07-07 11:47:40.816730190 +0100
@@ -1002,7 +1002,7 @@
   /** check if this opcode runs at perf time
   */
   bool is_perf() {
-      return this->opaddr ? true : false;
+      return this->opadr ? true : false;
   }
 
 };