msm: kgsl: Add supporting code for 2d dcvs

2d dcvs will also need changes in TrustZone.  However
by adding this code first the TrustZone update can be
made later without breaking any functionality.  This
feature is disabled by default and should not be
enabled without the necessary TrustZone changes in
place.

Change-Id: Ifdd511a3f18ba90faee189393ffc231fbbc6e2cd
Signed-off-by: Lucille Sylvester <lsylvest@codeaurora.org>