add ifdef guards on requested_size for bitmap requests

private-include/bitmap/bitmap_rb.h

@@ -47,7 +47,9 @@ typedef struct bitmap_rb_s {
 /** Chunk header data structure */
 typedef struct chunk_header_s {
     size_t num_of_cells; /**< The number of occupied cells. */
+#ifdef REQUEST_SIZE_INFO
     size_t requested_size; /**< The requested size. */
+#endif /* REQUEST_SIZE_INFO */
 } chunk_header_t;
 
 /** The size of the chunk header in bitmap-organised raw blocks */