drm_hwcomposer: Update external connectors list

DVID, DVII and VGA are required by discrete and integrated GPUs.

Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
diff --git a/drmconnector.cpp b/drmconnector.cpp
index 247f56b..145518f 100644
--- a/drmconnector.cpp
+++ b/drmconnector.cpp
@@ -73,7 +73,9 @@
 }
 
 bool DrmConnector::external() const {
-  return type_ == DRM_MODE_CONNECTOR_HDMIA;
+  return type_ == DRM_MODE_CONNECTOR_HDMIA || type_ == DRM_MODE_CONNECTOR_DisplayPort ||
+         type_ == DRM_MODE_CONNECTOR_DVID || type_ == DRM_MODE_CONNECTOR_DVII ||
+         type_ == DRM_MODE_CONNECTOR_VGA;
 }
 
 bool DrmConnector::valid_type() const {