idmap2: use 'override' where possible

Sprinkle idmap2 with the override specifier to help the compiler catch
future errors.

Test: builds
Change-Id: I6932c5a80ac607f310e256620194e04acfd19ffd
diff --git a/cmds/idmap2/idmap2d/Idmap2Service.h b/cmds/idmap2/idmap2d/Idmap2Service.h
index 1aab059..94d2af4 100644
--- a/cmds/idmap2/idmap2d/Idmap2Service.h
+++ b/cmds/idmap2/idmap2d/Idmap2Service.h
@@ -34,18 +34,19 @@
   }
 
   binder::Status getIdmapPath(const std::string& overlay_apk_path, int32_t user_id,
-                              std::string* _aidl_return);
+                              std::string* _aidl_return) override;
 
   binder::Status removeIdmap(const std::string& overlay_apk_path, int32_t user_id,
-                             bool* _aidl_return);
+                             bool* _aidl_return) override;
 
   binder::Status verifyIdmap(const std::string& overlay_apk_path, int32_t fulfilled_policies,
-                             bool enforce_overlayable, int32_t user_id, bool* _aidl_return);
+                             bool enforce_overlayable, int32_t user_id,
+                             bool* _aidl_return) override;
 
   binder::Status createIdmap(const std::string& target_apk_path,
                              const std::string& overlay_apk_path, int32_t fulfilled_policies,
                              bool enforce_overlayable, int32_t user_id,
-                             std::unique_ptr<std::string>* _aidl_return);
+                             std::unique_ptr<std::string>* _aidl_return) override;
 };
 
 }  // namespace android::os