Prevent VP8 encoding crash

This commit changes the value of highbitdepth flag to avoid conflict
with vp8 refresh_last_frame flag.

Change-Id: Idcff2cf44f0a200bd935b326f785c0cf32d7228a

vpx_scale/yv12config.h

@@ -61,7 +61,7 @@ typedef struct yv12_buffer_config {
   int flags;
 } YV12_BUFFER_CONFIG;
 
-#define YV12_FLAG_HIGHBITDEPTH 1
+#define YV12_FLAG_HIGHBITDEPTH 8
 
 int vp8_yv12_alloc_frame_buffer(YV12_BUFFER_CONFIG *ybf,
                                 int width, int height, int border);