drm/msm/sde: avoid VBIF programming during secure-ui session

Avoid all register programming related to VBIF during
secure-ui session when secure-ui-misr feature is enabled
as it would end up in SMMU fault.

Change-Id: I847242ed1b7c4ef0b86c198f5a252e8ba85c6458
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>