hwc: Avoid partial frame update on secure display

On configuring for secure display, MDP switches to secured
memory bank. Invoking any more DCS panel commands which
follows non-secure path will cause XPU violation. So its
necessary for HWC to turn off partial update to avoid DCS
commands due to ROI change.

Change-Id: Ibcc24d34d3cb825b027c116ac6a4d841d9cb9b70