ARM: dts: msm: Make Audio ION heap CMA heap for 8916

Currently Audio ION heap is CMA carved out and
thereby reserves memory out of the buddy allocator.
Make it to CMA heap so that the pages are returned
to buddy allocotar when Audio heap is not in use.

Change-Id: I581e3ef13147db5d93afe8f9cdd074102cba6943
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>