Refine async mode return value

BZ: 150664

Fix one async mode defect, use another error to identify work queue empty

Change-Id: I726d86153cff5c59e97ed98c063d8b002dadb0d8
Signed-off-by: Zhao Liang <leo.zhao@intel.com>
diff --git a/videoencoder/VideoEncoderBase.cpp b/videoencoder/VideoEncoderBase.cpp
index 4e49a40..0954fcc 100644
--- a/videoencoder/VideoEncoderBase.cpp
+++ b/videoencoder/VideoEncoderBase.cpp
@@ -426,7 +426,7 @@
                 }
             } else {//Nonblock
                 mEncodeTask_Lock.unlock();
-                return ENCODE_DATA_NOT_READY;
+                return ENCODE_NO_REQUEST_DATA;
             }
         }
 
@@ -476,9 +476,8 @@
                 mCurOutputTask->completed = true;
                 //if need to call SyncSurface again ?
 
-            }	else {//not ready yet
-                ret = ENCODE_DATA_NOT_READY;
-                goto CLEAN_UP;
+            }  else {//not encode complet yet, but keep all context and return directly
+                return ENCODE_DATA_NOT_READY;
             }
 
         }