gpu: ion: Add extra metadata for secure buffers

Newer versions of content protection allow for securing of individual
buffers instead of the full heap range. Add extra metadata about
each allocated buffer for tracking information related to secure
state.

Change-Id: I326ce35a17cd27b61831b0bde4e7423f1ac3d106
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>