EffectsFactory: fix subeffects loading

Due to a error in code, effects loaded via libproxy were
not populated correctly when the new XML effects format
was used.

Bug: 37492580
Test: no "AudioFlinger could not create effect" error messages
      when enabling effects in Play Music

Change-Id: I15b4f20060397662c98835cdf8af9fa198ea994f
diff --git a/media/libeffects/factory/EffectsXmlConfigLoader.cpp b/media/libeffects/factory/EffectsXmlConfigLoader.cpp
index 42e00f8..438b787 100644
--- a/media/libeffects/factory/EffectsXmlConfigLoader.cpp
+++ b/media/libeffects/factory/EffectsXmlConfigLoader.cpp
@@ -281,7 +281,7 @@
                 ++nbSkippedElement;
                 continue;
             }
-            listPush(&effectLoadResult.effectDesc, subEffectList);
+            listPush(effectLoadResult.effectDesc.get(), subEffectList);
 
             // Since we return a dummy descriptor for the proxy during
             // get_descriptor call, we replace it with the corresponding