hwc: Add secure display attribute

- External displays can be secure or non-secure based on HDCP
- Propogate this to the SF with the getDisplayConfig
- Non-virtual displays(pri and hdmi) are considered to be secure
- For WFD using V4L2 archiecture, read the HDCP status from the
  sysfs and update accordingly

Change-Id: I4aaf303f0770201b8ca4f8a1c578bed61054bcfb
Merge "hwc: Add secure display attribute"
Revert "hwc: Add secure display attribute"

This reverts commit 844848cb90836cc6c337fdae94eaabe5a8f52d3b

Change-Id: If212b3627fc5a9921a832b7bee2a946a60cf4746
Merge "Revert "hwc: Add secure display attribute""
Merge branch 'LA.BF.1.1_rb1.10' of git://codeaurora.org/quic/la/platform/hardware/qcom/display into lollipop