ivi-shell: remove struct link_layer

link_layer's sole purpose is to link a surface to multiple layers, if
the surface should be shown in multiple layers.  This can be only
achieved, if the surface has multiple weston_views with different
transformation matrices.

Current implementation assumes in many places that a ivi_surface has
only one weston_view.  Therefore, a surface can be only shown on one
layer.

Although this (a surface on multiple layers) is a nice to have feature
for ivi-shell, it is not very crucial.  In any case, it is not an easy
task to implement this feature, because it has lot of corner cases.

I removed with this patch the link_layer data structure, because it does
not have any purpose in current implementation.

Signed-off-by: Emre Ucan <eucan@de.adit-jv.com>
Tested-by: Nobuhiko Tanibata <NOBUHIKO_TANIBATA@xddp.denso.co.jp>
Reviewed-by: Nobuhiko Tanibata <NOBUHIKO_TANIBATA@xddp.denso.co.jp>
[Pekka: Line-wrapped the commit message.]
diff --git a/ivi-shell/ivi-layout-private.h b/ivi-shell/ivi-layout-private.h
index a9dbdde..3244390 100644
--- a/ivi-shell/ivi-layout-private.h
+++ b/ivi-shell/ivi-layout-private.h
@@ -32,11 +32,11 @@
 struct ivi_layout_surface {
 	struct wl_list link;
 	struct wl_signal property_changed;
-	struct wl_list layer_list;
 	int32_t update_count;
 	uint32_t id_surface;
 
 	struct ivi_layout *layout;
+	struct ivi_layout_layer *on_layer;
 	struct weston_surface *surface;
 
 	struct weston_transform transform;
@@ -65,7 +65,6 @@
 struct ivi_layout_layer {
 	struct wl_list link;
 	struct wl_signal property_changed;
-	struct wl_list link_to_surface;
 	uint32_t id_layer;
 
 	struct ivi_layout *layout;