ivi-shell: describe members of type wl_list

I wrote comments on which list they are used with

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
[Pekka: fix surface_list to layer_list, add ivi_layout_transition_set::transition_list]
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/ivi-shell/ivi-layout.c b/ivi-shell/ivi-layout.c
index fee508d..60d05c4 100644
--- a/ivi-shell/ivi-layout.c
+++ b/ivi-shell/ivi-layout.c
@@ -76,18 +76,18 @@
 struct ivi_layout;
 
 struct ivi_layout_screen {
-	struct wl_list link;
+	struct wl_list link;	/* ivi_layout::screen_list */
 
 	struct ivi_layout *layout;
 	struct weston_output *output;
 
 	struct {
-		struct wl_list layer_list;
+		struct wl_list layer_list;	/* ivi_layout_layer::pending.link */
 	} pending;
 
 	struct {
 		int dirty;
-		struct wl_list layer_list;
+		struct wl_list layer_list;	/* ivi_layout_layer::order.link */
 	} order;
 };