av: change return value if effect is not processing

Return -ENODATA in case if effect is not processing
so AudioFlinger can stop calling process on the effect.
Otherwise, AudioFlinger will retry for a disable count,
causing no sound for that period.

Change-Id: Ie987e6384b87e720b3fd569e242f6b8c3ae11e31
diff --git a/media/libaudiohal/impl/EffectHalAidl.cpp b/media/libaudiohal/impl/EffectHalAidl.cpp
index 642d352..f26444c 100644
--- a/media/libaudiohal/impl/EffectHalAidl.cpp
+++ b/media/libaudiohal/impl/EffectHalAidl.cpp
@@ -173,7 +173,7 @@
               mConversion->isBypassing()
                       ? "bypassing"
                       : aidl::android::hardware::audio::effect::toString(state).c_str());
-        return OK;
+        return -ENODATA;
     }
 
     auto statusQ = mConversion->getStatusMQ();