avutil/buffer: add #if USE_ATOMICS around atomics specific functions to ensure sync types arent mixed by mistake

Fixes CID1257011

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

libavutil/buffer.c

@@ -250,6 +250,7 @@ void av_buffer_pool_uninit(AVBufferPool **ppool)
         buffer_pool_free(pool);
 }
 
+#if USE_ATOMICS
 /* remove the whole buffer list from the pool and return it */
 static BufferPoolEntry *get_pool(AVBufferPool *pool)
 {
@@ -285,6 +286,7 @@ static void add_to_pool(BufferPoolEntry *buf)
             end = end->next;
     }
 }
+#endif
 
 static void pool_release_buffer(void *opaque, uint8_t *data)
 {