Using a LIFO instead of a FIFO has the potential benefit that more
recently in-use buffers may be "cache-hot" and therefore accessed
faster than least recently used (which is what we get with a FIFO).
Change-Id: I59bb083ca2e00d0d404406540f7db216742a27cf
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>