BufferQueue returns proper code on acquire

Also removed unnecessary debug messages from
SurfaceTextureClient.

Change-Id: I291897a44170142f9d42a007b008823fad4683e0
diff --git a/libs/gui/BufferQueue.cpp b/libs/gui/BufferQueue.cpp
index 84ccb3f..8263e4e 100644
--- a/libs/gui/BufferQueue.cpp
+++ b/libs/gui/BufferQueue.cpp
@@ -851,8 +851,7 @@
 
         ATRACE_INT(mConsumerName.string(), mQueue.size());
     } else {
-        // should be a better return code?
-        return -EINVAL;
+        return NO_BUFFER_AVAILABLE;
     }
 
     return OK;