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.h b/drmresources.h
index 011f87e..5cca11b 100644
--- a/drmresources.h
+++ b/drmresources.h
@@ -68,6 +68,7 @@
   int GetConnectorProperty(const DrmConnector &connector, const char *prop_name,
                            DrmProperty *property);
 
+  const std::vector<std::unique_ptr<DrmCrtc>> &crtcs() const;
   uint32_t next_mode_id();
   int SetDisplayActiveMode(int display, const DrmMode &mode);
   int SetDpmsMode(int display, uint64_t mode);