hwcomposer: Add HWC_DISPLAY_SECURE as a dpy attribute

- HWC_DISPLAY_SECURE attribute will be used by SurfaceFlinger
  to determine if the display is secure.
- This property will be set to true if the display is secure based on HDCP

Change-Id: I9c01239521e81ae3d863e9bfbba0de72264dc14c
1 file changed