ion: Add support for ION_AUDIO_HEAP_ID

Audio team have decided that they do need support for the audio heap.
So add back support.

Newly added heap ids have to be #define(d) since all API changes must
include a new #define.

Change-Id: Ib2c8214e171591d68287a4fdb9456bf38186459e
Signed-off-by: Liam Mark <lmark@codeaurora.org>