hwc: Rename app buffer count property

Renaming app buffer count property based on
naming convention of android.
CRs-Fixed: 764611
Change-Id: Ic627668752542b797c6b1313adb1e1ca195c0609
diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 9ea8246..1ac4153 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -75,7 +75,7 @@
 #endif
 #endif
 
-#define PROP_DEFAULT_APPBUFFER  "sf.default.app_buffer_count"
+#define PROP_DEFAULT_APPBUFFER  "hw.sf.app_buff_count"
 #define MAX_RAM_SIZE  512*1024*1024
 #define qHD_WIDTH 540