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
diff --git a/libhwcomposer/hwc_utils.h b/libhwcomposer/hwc_utils.h
index 96d1e58..c95c59c 100644
--- a/libhwcomposer/hwc_utils.h
+++ b/libhwcomposer/hwc_utils.h
@@ -89,6 +89,7 @@
     uint32_t stride;
     float xdpi;
     float ydpi;
+    bool secure;
     int fd;
     bool connected; //Applies only to pluggable disp.
     //Connected does not mean it ready to use.