display: Various cleanups, fix legacy camera heap

 * Add explicit support for camera heap, if requested
 * Bring in line with kk_2.7
 * Don't push to MM heap for NO_IOMMU for display buffers

Change-Id: I30a8280099aa82e9b3e9754a4a68ad6a81f705f7
gralloc: Allow legacy devices to use PMEM for ADSP (camera).

Partially bring back PMEM support for legacy devices having proprietary camera
libraries stuck in PMEM. This change allows these devices to continue using
PMEM for the camera, and ION for everything else.

Change-Id: I1afbc7d137b3d49b2ab3e53917b16fd920ea140b