VAAPI: We can use less GPU surfaces.

modules/codec/avcodec/vaapi.c

@@ -235,7 +235,7 @@ static int CalculateSurfaceCount( const int i_codec_id )
         return -1;
     }
 
-    return 20 /* VOUT_MAX_PICTURES */ + i_count * 2;
+    return 20 /* VOUT_MAX_PICTURES */ + i_count;
 }
 
 /* */