libaudiohal: Fix EventFlag leak

Add EventFlag deletion in the effect wrapper's destructor.

Bug: 64495982
Test: make
Change-Id: I3a5bbe36ce064468790c35259aa621e1012ddcb6
diff --git a/media/libaudiohal/EffectHalHidl.cpp b/media/libaudiohal/EffectHalHidl.cpp
index b49b975..48d3a32 100644
--- a/media/libaudiohal/EffectHalHidl.cpp
+++ b/media/libaudiohal/EffectHalHidl.cpp
@@ -49,6 +49,9 @@
         mEffect.clear();
         hardware::IPCThreadState::self()->flushCommands();
     }
+    if (mEfGroup) {
+        EventFlag::deleteEventFlag(&mEfGroup);
+    }
 }
 
 // static