msm: mdss: add secure display support

Secure display architecture requires null commit
before and after secure display session. It
also adds requirement to make the SCM call before
and after secure display session. It supports secure
display with single-stage SMMU hypervisor controlled.

Change-Id: I3f41ed318c80d6e76328de114f7dee0c9891c2f0
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>