avutil/buffer: remove redundant memory poisoning

Found-by: ubitux
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/buffer.c

@@ -71,9 +71,6 @@ AVBufferRef *av_buffer_alloc(int size)
     if (!data)
         return NULL;
 
-    if(CONFIG_MEMORY_POISONING)
-        memset(data, 0x2a, size);
-
     ret = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
     if (!ret)
         av_freep(&data);