drm_hwcomposer: Add crtc() fetcher to DrmResources

This is a fetcher for getting the vector of DrmCrtc objects
in DrmResources.

Signed-off-by: Robert Foss <robert.foss@collabora.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
diff --git a/drmresources.cpp b/drmresources.cpp
index 6b8ed03..ea23cce 100644
--- a/drmresources.cpp
+++ b/drmresources.cpp
@@ -245,6 +245,10 @@
   return NULL;
 }
 
+const std::vector<std::unique_ptr<DrmCrtc>> & DrmResources::crtcs() const {
+  return crtcs_;
+}
+
 uint32_t DrmResources::next_mode_id() {
   return ++mode_id_;
 }