expo: Rename scene_dim to scene_obj_bbox

At present we assume that each object is a simple box and that it fills
the whole box.

This is quite limiting for text objects, which we may want to centre
within the box. We need a position within the box where drawing starts.

Rename the scene_dim struct to indicate that it is a bounding box.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/scene_menu.c b/boot/scene_menu.c
index 6a2f5b6..20a6a6b 100644
--- a/boot/scene_menu.c
+++ b/boot/scene_menu.c
@@ -102,7 +102,7 @@
 		label = scene_obj_find(scn, item->label_id, SCENEOBJT_NONE);
 
 		ret = scene_obj_set_pos(scn, menu->pointer_id,
-					menu->obj.dim.x + 200, label->dim.y);
+					menu->obj.bbox.x + 200, label->bbox.y);
 		if (ret < 0)
 			return log_msg_ret("ptr", ret);
 	}
@@ -186,8 +186,8 @@
 	}
 
 	if (bbox.valid) {
-		menu->obj.dim.w = bbox.x1 - bbox.x0;
-		menu->obj.dim.h = bbox.y1 - bbox.y0;
+		menu->obj.bbox.w = bbox.x1 - bbox.x0;
+		menu->obj.bbox.h = bbox.y1 - bbox.y0;
 	}
 
 	return 0;
@@ -205,12 +205,12 @@
 	int x, y;
 	int ret;
 
-	x = menu->obj.dim.x;
-	y = menu->obj.dim.y;
+	x = menu->obj.bbox.x;
+	y = menu->obj.bbox.y;
 	if (menu->title_id) {
 		int width;
 
-		ret = scene_obj_set_pos(scn, menu->title_id, menu->obj.dim.x, y);
+		ret = scene_obj_set_pos(scn, menu->title_id, menu->obj.bbox.x, y);
 		if (ret < 0)
 			return log_msg_ret("tit", ret);