drm_hwcomposer: Add connection state to DrmConnector

So we can determine if it's connected or not.

BUG=chrome-os-partner:41682
TEST=Tested on ryu with DP

Change-Id: Ie0dadb2737d3a98257fb6e4fa02f17d7dae44f6c
Signed-off-by: Sean Paul <seanpaul@chromium.org>
diff --git a/drmconnector.h b/drmconnector.h
index 3c9eca0..e1488bb 100644
--- a/drmconnector.h
+++ b/drmconnector.h
@@ -63,6 +63,8 @@
   DrmEncoder *encoder() const;
   void set_encoder(DrmEncoder *encoder);
 
+  drmModeConnection state() const;
+
   uint32_t mm_width() const;
   uint32_t mm_height() const;