hwc: increase app buffers to 3 on 8909_512
increase the app buffers to 3 to improve the performance
of the Ux scenarios.

Change-Id: Ie413213baa7bbd6777f42e78842975852e34ea45
diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 9ea8246..75b365d 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -261,7 +261,7 @@
     }
     if ((ramSize && ramSize < MAX_RAM_SIZE) &&
          (sInfo.xres &&  sInfo.xres <= qHD_WIDTH )) {
-                  property_set(PROP_DEFAULT_APPBUFFER, "2");
+                  property_set(PROP_DEFAULT_APPBUFFER, "3");
     }
 }