mach-msm: Use ION_CP_MM_HEAP_ID instead of ION_CAMERA_HEAP_ID

Since some msm7x30 devices can't use ION_CAMERA_HEAP_ID on rom side,
we have to change the ion heap used for video encoding/decoding from
ION_CAMERA_HEAP_ID to ION_CP_MM_HEAP_ID.

On rom side, the following commit must be applied on media-caf side:
http://review.cyanogenmod.org/#/c/62863/