When a heapbuf object is created, there are two memory buffers allocated -- one
for the handle and one for the object itself.  That is in _heapbuf_create.  In
heapbuf_delete, both are freed.  But in heapbuf_close, only the handle is freed.
The object pointer is not freed and caused a memory leak.  This patch adds a
call to free the object.
Signed-off-by: Simon Que <sque@ti.com>