Don't force GPU composite for older devices

Older devices (8960) don't take this very well in programs like
Netflix. Modeled on 94b8632b85e2b6588a1b3260d1f4e48462501d4b

Change-Id: Ie716bbfb6f6560d8f9f52b7b72ca0b04d1bad6b8
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